DeadEyes: It's pretty funny that you bring up the engines. By the way, be sure to post some video on your flight with your buddy! I was doing some searches and came across this scratch built DH-2 with a rotating engine. I thought is was photo-shopped and emailed the owner, Ian, and this is what he told me:

Hi Charles, my DH2 was scratch built by myself and Kevin Wesley, started back around 2000. It was drawn up using the Windsock Datafile. The motor is a Zenoah 62, with a 1.75 to 1 belt reduction drive and a 9.5" extension shaft to get the heavy bits infront of the CofG. It also allows it to swing a home made 30" x 14" scale propeller. The dummy motor does indeed rotate. It freewheels on a bearing off the propshaft. The dummy motor itself is made out of foam, blue foam for the crankcase and cast 2 part foam for the cylinders. The dummy motor is extremely light so doesn't load up the Zenoah much. Heres some pics

I posted the pics he sent me below. I may mold a Williams Bros. 1/6 scale engine and attempt to make a foam twin as the foam can be shaved to fit in the cowl and painted. I've also come across threads where plastic was turned to replicate the engine, however; it didn't rotate. First things first, I want to get access to several units so I can break them and try again...so that is the reason for me looking into molds. One of my side projects is to replicate something like that. I've been doing research on molds and foams, so we shall see! It just seems like it can be done.