stepped piston engine

Is this the crowd who used to be based in Bath, and had a Peugeot 205 running with one in the late 80s ?

It seemed like the most promising way to make a small car two stroke with decent emissions. I forget why now, but this was going to be significant and we'd all be driving them within a few years (Orbital, Ford, Jaguar)

The downside for a car was that it vibrated a bit (heavy pistons) and wouldn't rev, and that the porting was a little long and thin. It seemed to get overtaken by better catalysts and EMS. For UAV engines, I imagine it's ideal.