I have the Aviomodelli Skymaster ....... ARF???....... myself. What a shock when I received it. I ordered the Cant Z tri-engine bomber as well. I think the Italians have a strange idea of 50% arf.[X(] No, it isn't finished yet
Anyway......
I wouldn't put anything less than 91 4 strokers. I fly my friends KMP sky master and the strokers are the correct power as far as I'm concerned. Especially if I were to fly from a rough grass field. You need the torque and reserve power for single engine operation and I've had to fly on one engine. I was even able to takeoff - marginally- with the rear engines prop on backward. Always double check that rear prop when you replace it for any reason. Even when you trust the person who did it!. The point is that the extra power is very important in an emergency. At our field we have horrible rain ditches just pass the end of our runway. A real killer if you can't get down fast enough after a engine failure on take off!