I usually do my due diligence and search first and there are a lot of hints that I found

BUT I would still like to ask a question or two

To date I have just lived with recommended factory mufflers, never bought any lite tube types

Recently I did get some engines with Tongue mufflers.

Most are NOT tapped and fitted for pressure fitting..

Each has pre drilled exhaust holes.... but the number and size--- is not to me--- consistent within a engine size, some have 5 or 6 bigger holes others 10~14 smaller holes

I am very lucky ---OR you guys have so much good free advice that each plane, prop, engine, tank, venturi, NVA mix that I have set up---each has worked just about perfect for me first time out... very minor fiddling with line length, prop and fuel mix

Of course I am a pure hack, and probably would not recognize a good stunt run if it bit my butt but so far...all my engines start, are set to a recommended RPM, launched, and fly out the tank with NO drama, burps, run away ....I used to fly combat so really can recognize a very lean 12 minute engine cooking run...in fact put a few in the dirt to save the engine

The Fox 35 (no burp plug) is my only one with a pronounced 4-2-4 that is pretty cool to experience... the BBTU OS, .20~.25 to LA/FP 40s and 46s just churn along going pretty good up hill and settling back stable down hill and level

I have one or more ARFs and other bigger planes planned that I might need to consider the Tongue mufflers just for weight and balance reasons

MY searching suggest where the pressure nipple is located--- is just a matter of anywhere that makes sense for the line routing....
True?
Or is there some optimal location?

What I am really uncertain of, is how to evaluate a particular engine to determine if IT needs more or larger holes, or some closed in

Current never used Tongue / chip mufflers
Evo .36
Lew Woolard Fox .35 and Fox .40
Stock LA .40 .46
RS B&B LA .46
Tom D modified OS FP 40

The Magnum .52 I got from Randy for a ARF SV 11 came with the porky factory Muff and I know he has lighter tube or tongues for it

Thoughts
Opinions
advice sought

Sport flyer hack with NO desire nor ability for overhead 8 and/or 15 G sharp square corners

                   The questioning seems to be all over here. What are you really trying to decide? You mention several engines and it seems your in search of how many holes are needed? If your flying level and a occasional loop here and there, your not going to load the engine enough to determine if your in need of a less restrictive exhaust. Fox .35's in general don't tolerate exhaust well. I use them but depending on the plane and weight of the plane, this could prove to overheat the engine and cause it to sag if not seize all together. The other side of this is that sagging on the Fox is not always diagnosed correctly therefore it could be several things, a poor needle setting, muffler too tight, bad tank, poorly built tank,  the fact that it's a Fox and it's internal parts were made with stone tools, head screws incorrectly torqued twisting the case, a bind in the engine etc.

              The Evo .36 has very restrictive holes in my opinion and not enough of them. You apparently haven't used this engine so I won't elaborate on that but I myself prefer the manufacturers to leave the muffler in the state it was constructed so that I can alter to suit my needs.

               Your questioning isn't one that can be answered over the internet directly as this is something that dictates experimentation. You make no mention of props which is a big factor here. Are you using props of the incorrect pitch? Where in the flight do you feel your engine is overheating or possibly lacking? What type of tanks are you using and exactly what are you experiencing? Certain tank manufacturers are notorious for problems and during the course of your engine run, you might be diagnosing certain conditions as over heating when your tank is not feeding correctly due to splits in the pickup internally or leaks or possible corrosion inside.

              If your not experiencing issues, why request more holes or less for that matter? Flying the pattern can offer some benefits due to the fact that you can lend advice as to where the problems begin. Essentially if one claims that he's experiencing problems when he enters the overhead, it's very clear that his fuel load is not the same as when he launched and it's not shortly after launch so we can build a time frame into the flight .

        Every engine is different, every plane weight is different. Your not going to be able to throw out a number here and expect stellar results due to so many variables. You being in Texas presents even a further issue in terms of temperature. In general, I place the nipple perpendicular to exhaust flow, I don't place it parallel or inline with the exhaust to where fluids can settle into the nipple possible clogging it. I don't concern myself with what side it's on unless it's interfering with tubing routing from the tank. On profiles, due to our muffler rules at our field, I have the holes pointing towards the pilot and not facing out . I sometimes feel this keeps the noise from being louder vs the other way. I haven't been outside of the circle to verify if this works but I flip flop this from time to time with no ill effect. Ken

Fred, I've asked a broader question in the past—one based on the multitude of different outlet diameters on tube/expansion mufflers of various types.

I cannot find any rhyme or reason behind the outlet diameters and therefore, outlet areas.

For example, if I remember correctly, Randy's tube mufflers for the FP 40 and FP 20/25are the same diameter and have the same size outlet but the 40 item is longer/has a larger volume.

The factory muffler for the Thunder Tiger GP 40 is a similar size to the 3030 muffler for the FP 40 but has an outlet diameter almost 2mm larger but then, Thunder Tiger supplied the same muffler for their hotter 25.

I take several mufflers with me the first time I take out a new model/engine combination and find what works best.

No logic and no science, but it seems to work.

Thanks Dane.. Since I do have a good enough (tach) and a good HF Laser Temp gun---- that is exactly what I was thinking I might do

Like I said (convoluted above) was hopefully someone would chime in and say... hey that XXX muffler with only 5 holes has always been too restrictive on That XXX engine....so open them up some

Over the years I got extremely lazy because all the advice on these sites has let me learn, pick a system of components, throw them together and (SO FAR) experience some what predictable results

Like so many set up recommendations for a engine, Tank, fuel, prop recipes that a lot of different folks claim ALWAYS works

MY total experience to date has been real problem free

So for my hacking around in the sky at the well documented lower end (RST/Nobler/RingMaster/Skyray/Twister) with near perfect copied systems has been real fun and rewarding

Moving up to larger Flapped and perhaps ---way above my skill level---- Like P40/Oriental/SV-11 planes and engines--- had me a bit intimidated...because, as stated elsewhere, I truly still do NOT know what Right Looks and Feels like

I'm not sure why I'm having such a hard time answering this. Lol. I'm going over and over what I'd like to say, but somehow every answer I can think of, I know someone will jump in and say how incorrect these figures are. But, I guess here goes.....
I once talked on the phone with the guys at thunder tiger about a heli engine. They said 305 degrees at the glo plug. I thought that sounded a little high. I've had engines sound great, have plenty of power and come down at 180 degrees. That is a little cool. Very rich run, I would think you could get more power. But it seems we run a very powerful engine "detuned".  Whereas the power only comes on in the up lines. So I will answer your question as it pertains to sport / stunt with 180-240.
After the engine dies, land the plane and get out to it quickly. You should be able to hold your finger on the back plate for around  3 seconds or more. If it leaned out and you get those last 10 or 20 lean laps and that's why is hot, fix your tank and get a clean shut off, otherwise none of this matters. It'll always be "too hot". I hope this sounds reasonable, and not rambly.... lol