The OS FL-70 runs pretty good and is still available. It does have a couple drawbacks though in my opinion. For one, you can't flip the carb around so that can make the throttle linkage difficult. Number 2 is the air bleed carburetor. Mounted upright or sideways, it works fine but upside down can be a nightmare. There is no way to adjust fuel on the low end, just air. Unless the tank is positioned just right, it will tend to run very rich so you have to open the air bleed screw to compensate. That in turn leads to a high idle.

I agree that the .80 size engines are probably overkill for a lot of 40 size planes but it looks like that's the way the manufacturers are going.

Traski indicated the engine would go on a 40 size Stik. I wonder how OS's new .56 would do? I've seen the older .52's fly a 40 size plane around pretty good. Not quite equal with a .70 but still respectable.