RE: ENGINE SIZE ?
I have a PT 40 with a Saiito 45 in it. The plane flew with authority. I liked it. I dorked the plane and damaged the motor. I will some day send it out and have it repaired. I think that engine will do great in the Kadet. The GB Cub will work good but if you want airobatics I would opt for a bigger engine. Maybe a 52 or even a 70 saito. I am building the GP Cub and am stuffing a Saito 80 in it with the full wing. I know it will be overkill but I have one and the kit states an 80 will be ok.
Mark Shuman