Charles, I also thought about doing a rotating engine but decided that idea needed to wait a while. WWI era rotary engines spun at around 1,500-2,000 RPMs. In contrast, our model engines would be spinning a dummy engine at up to 10,000 RPMs. At that speed a dummy would just be spun to pieces.

So there seem to be two main solutions. One, as on Ian's stunning DH2, people use a belt reduction system allowing a larger (scale) prop and slower speeds. The other solution is to not have the dummy connected directly to the engine but instead to allow it to "pinwheel in the breeze." This would seem like the only possibility on an EIII.

Also, a note on the WB 1/6 scale Le Rhone kit. It is WAY undersized for a 1/6 scale EIII with a scale sized cowl. I'm not sure why. But the diameter is a good inch too small. Also, of course, it's a Le Rhone and not a Gnome/Oberursal engine. For my dummy I ended up heavily modifying one of the kits. I started by extending the length of each of the cylinders with styrene. Then I used the crankcase backplate for the front and then modified that to look more like the Oberursal. I also scratch-built new rocker heads and rods. I think there's a couple photos of it in the link I posted above.