EPP is expanded polypropelene. It was first used in R/C airplanes for slope soaring, and tufflight introduced it for fuel power planes 4 years ago. It makes planes bounce when they hit something.

UHMW is ultra high molecular weight polyethelene. It's practically the same plastic used for fuel tanks. Think CUTTING BOARDS -- super tough, and hard to break-- they bend. Tufflight introduced this to the combat world 4 years ago as well.

You're right- RPM and speed is not everything. All planes slow down in turns, and you need to manage energy. A dream engine pulls really hard all the time no matter what throttle setting you have. You are limited in speed by the need to stay below "streamer shredding" speed.

Norvels are the best power to weight around (see picture above) and a stock .25 will run really good with an APC 8x5 prop. 18.5K RPm is usual with this combo. If I use tuned mufflers, I like the Master airscrew 9x4 prop, and a good Norvel (they aren't all created equal) will turn a MA 9x4 prop at 19.2K RPM, and a great one will go over 20. The MA props stay together much better if you hit someone else -- the APC's tend to shatter, but they do give more thrust.

For more info on combat, and state of the art stuff, you really should check out the RCCA website:

www.rccombat.com

Didn't mean to turn this into a combat commercial, but, hey, you asked...