I'd also like to see pictures of the converted engine and see the steps involved. Used ST90s are cheap; it may be worth a try.

Remember that the BME engine has a new crankshaft, piston and needle bearing rod, all designed specifically for gas. It's also got a gas carb and has had the case machined for the timer assembly. It may be comparing apples and oranges to compare a ST90 with an electronic ignition to an engine where all the moving parts and fuel system are different. Other than the case and head, there's not much ST left, and those remaining parts have been modified.

The proof, of course, is in the running and the longevity as well as the price you're willing to pay. I run my old Cyclone and O&R 60 on 3:1 gas and oil. I'd like to see how long a bushed rod would hold up at 20:1. Maybe with light loads and short runs it could last a long while, or maybe you run it at 10:1 and give up some power. I don't know.

Jim