I have never owned any of these brands but surely have heard of the names but need your reviews or comments on them.
First one is the OS max .15, the os max .25, and a thunder tiger .15. I would be using them in control line planes.  Also how much difference is there between the os max .15 and the os .20  these are the FP versions.   Also have to ask about the K&B .25 sportsters.
Thanks

I have never owned any of these brands but surely have heard of the names but need your reviews or comments on them.
First one is the OS max .15, the os max .25, and a thunder tiger .15. I would be using them in control line planes.  Also how much difference is there between the os max .15 and the os .20  these are the FP versions.   Also have to ask about the K&B .25 sportsters.
Thanks

    A 20FP is substantially stronger than a 15FP, as you would expect. Same with a 25FP, stronger than both, and all of these engines are much, much stronger than their vintage counterparts. The 25LA is also a very good engine. I think the 20FP and the 25LA are extremely good stunt engines on most 35-sized profiles, and require *no* modifications, you use them exactly as they come out of the box, muffler, everything. So all you have to know to get the best performance is to *leave them alone*, and don't let anyone else "improve" them for you.

    A 15FP is acceptable on a full-size Ringmaster if you know what you are doing otherwise. A 20FP is really too powerful and will pull a Ringmaster or similar faster than most people are comfortable with, but if it's off a little bit, it will certainly still fly the airplane.

    A 20FP, 25FP. or 25LA will fly most "35-sized" trainer airplanes like the Skyray 35, Flite Streak (full-size, not the 15-sized version!), Twister, etc. *much much* better than they flew when they were designed around Fox 35s and the like. Engines have gotten vastly more powerful for their size since about 1980 or so, so you use a smaller engine than you used to.

   If you have a specific application in mind, we can probably help steer you in the right direction. It probably doesn't matter at this point what type of CL category you are interested in (combat, stunt, carrier, etc), you still want to develop your basic flying skills and then decide what you want to do beyond that later.

   Brett

Matt, Bret, thank you guy's for your input and taking the time to inform me on these.    I have picked up a .15 Max OS,   and  .25 Max os FP.  The .15 is an older model but has ver little use and is in great shape, will use it for .15 size c/l.  The .25 is also in very good shape and looks to have little use, i will be installing venturi's and nv on these. The .25 will go on my next 35 size plane whatever that will be.
Thanks again.

Jim< this is what I think is so funny,   :all of these engines are much, much stronger than their vintage counterparts. : Of the engines mentioned, I can not think of a one that will turn a 10 x 6 prop at 9500 RPM and fly a 50 ounce stunt plane.
The new engines make their power by turning alot of RPMs and running flat pitch props.  Any erngine that you can get to run to suite you is a good engine and there is no sense in denigrating any others.    Phil

Brett get you story straight, I never said that a heavy piston gives more torque.  I said that there is a range of weights of pistons that will work in a given engine depending on the end use of said engine. For a stump pulling 4 2 4 style of stunt run, the upper end of that range is usable, for a high rpm style run, the lower end of that range is usable. That is all that I said. A basic knowledge of mechanics and physics should affirm that,  Again which of those engines that you mentioned will turn a 10 x 6 at 10000 rpms and fly a 50 ounce stunt ship?  Phil