I was thinking something along the same lines. I have a home built ultralight airplane from the 1980s called a Skypup. Mine has a Rotax 277 which was originally designed for snowmobiles. It runs at a high RPM so it has a gearbox which reduces the speed to something suitable for a small propellor. I had so many great adventures in that little airplane.
My first thought was that the engines on the Shahed drones and the even cheaper decoys with foam airframes would likely be excellent powerplants for ultralight aircraft. With 3 gallons of gas, I could fly nearly a hundred miles with a low throttle setting.
