Hi Gil
These are terrific engines. They're not at all heavy, and you could happily use one in something as small as a (rather overpowered) Ringmaster or Flitestreak. Alternatively, any .35-size classic ship would be fine. Mine is in a 'Miss BJ', which is about 520 sq.in and 37 oz, and has never felt like it needs more power.
My setup is: stock venturi and muffler; Enya #3 plug; APC 10.5x4.5, launched at about 10200 rpm. Enya's recommended prop is a 9.5x6, which is ok if you want to fly briskly. They don't seem particularly fussy about fuel - I use 5/11/11 on uniflow with good results.
Apparently they can be run in a 4/2 (with something like a 10x6), but I haven't tried this and believe a wet 2 is preferable. Run like this, it's dead consistent. I get a slight power-up in sharp corners, but otherwise totally constant rpm from start to finish. Not a lot to complain about, really.
Steve