I purchased four tongue mufflers from stanleyf770's ebay store (he advertises on F@ceb00k as well).
I'm sharing what I've found during fit-checks.
In all, it looks like he's put a lot of work into getting the shapes right! The machining looks good in all but one case.
I've NOT put these on running engines yet; that may come later.

Fox 15
Very nice fit! I have the version in which he cuts away a slot to accommodate the Fox 15 muffler bosses.
12 holes drilled to #51, 0.0670” = 0.042 sq” exhaust area

Fox 35,
Very tight on Fox 35 stunt, can be tapped on. Good fit!
(Does NOT fit Fox Rocket, but then again it's not supposed to, I guess)
19 holes #48, .0760” = 0.0862 sq” exhaust area

McCoy 35 Red Head
Fits McCoy 35 Red Head well.
Also fits McCoy 40 Red Head but needs notch to be cut out of bottom (to clear boss on case)
Des NOT fit older McCoy 36 (too small).
19 holes #48 for .0862 sq”

OS Max 35
He sells this for the "OS MAX 35"; I have a MAX-H. The fit is very tight and should work, but the OS MAX-H 35 has a boss on the case below the stack. The muffler would need a slot ground in to fit.
25 holes at #48 for 0.113 sq”.
On this muffler, one of the side walls is only .045” thick which is too thin for proper set screw thread engagement.
The setscrews are 4-40 with thread pitch of .025”, so there's less than 2 threads engagement. That side will most assuredly strip out. I may try a JB-Weld build up to help support the setscrew.

I'm interested to hear if anyone has actually run these for a while to learn how well the set-screw attachment method works as compared to a strap.

 

I have seen these tongue mufflers but have been hesitant to get one due to the setscrew attachment method. These older engines (Fox & McCoy's for example) vibrate quite a bit. Seems to me a setscrew design is not all that secure. But I have no direct experience.

I also would like to know if others have any direct operational experience w/ Fox 35's and McCoy 35's.

Thanks

    I intend to try some of his mufflers. I like the set screw option. Install the muffler, tighten the screw, then remove the muffler. The set screws will leave a witness mark. Right on this witness mark, drill a shallow hole to make a dimple, or even drill it all the way through. Attach the muffler, and when sure of everything, put a dab of epoxy or C/A on the screw head to keep it from backing off. I think that will work fine. If still squeamish about it , use the screw holes as an anchor for a retaining spring that goes around the crank case. That will give in a crash and should not cause any damage,
  Type at you later,
   Dan McEntee

I received my Stanleyf770 tongue muffler for the McCoy 35 on my Ringmaster Sportster. Have had a few flights and no issues so far. Mufflers seem fine. As extra assurance I did drill small notches on the engine exhaust for the set screws to 'bite'.