Hadn't thought about that volfy...
For the 1.20 Katana threre's really no "perfect" converstion style motor that I can think of for this plane that would make it perform up to it's aerobatic potential.

HOWEVER, for a bit more money and less fussing with a conversion I'm totally blown away with how my little RCS 1.40 performs.

I'm currently running my RCS on a 13 lb H9 Edge with a Bambula 16x8. It pulls it around just fine....I have enough vertical to not even worry..pretty much unlimited vertical if I enter the up-line with some sort of airspeed. Crawls out of hover....I'm more impressed with the motor than the plane that's for sure...It's very "scale-like" in power to the full size Edge. Which by any means is not too shabby!!

I run a smaller 8 oz tank and have yet to run out of fuel even after 15 min flight.

To avoid the extra weight of an engine mount, maybe the FPE 1.3 is a decent choice....I haven't heard much about this motor though. There's also the newer Zenoah G-26...but I think it's a little heavier.

I would agree though, for even the small Poulan...you need 1100 square inches (min) of wing for good flight performance. Keep it under 10 lbs and the RCS is awesome....

So, that's kinda what I'm looking for now...an ARF that will build up less than 10 lbs with RCS 140 attached and more than 1100 sq in. Yet, still "scale-looking" aerobatic.

That would give me 1.5-1 thrust ratio.

Best of luck!
CrazyHerb