Mac's B-29 has 4 large gas operated engines, and hauls the X-1 up to altitude before dropping it into a glide. The power for the X-1 is an Estes model rocket engine with a plugged end, as it doesn't have to eject a chute like a model rocket would. He does this demonstration regularly at some events at Hogges Field, home of the SouthEastern Electric Flight Festival and sometimes the Joe Nall Giant Scale events in Georgia.
To answer some of the questions regarding sound,.. there is now a system that uses small 4" speakers and an amplifier in the cowling of some electric models to simulate real radial sounds. This is also variable depending on the throttle position of the model. If you search on YouTube for a "Corsair with Bendini Sound Module" you should be able to pick up a link for an English gentleman that has done this and shows it in the video. Really neat.
I've been flying RC for 15 years,.. and now finally getting into GA with my training. My most time consuming, and costly, project was my 65" wingspan 9lb Corsair. There are air operated retracts, flaps, full cockpit, and other details. I modeled it after the fighter squadron VF-17, and have the names of those KIA or MIA on the tail.
You can see a video of this, and my RC Dehaviland Beaver, on my YouTube Site -->
http://www.youtube.com/watch?v=iy7DUIJ7zws
Rob