The saito 90 radial would probably fly it if you keep it light, but it would be close. I belive if you search some people have flown the Hangar 9 Corsair (Same size as the Top Flite, but usually lighter) with that engine. The 170 would be too big for the cowl. I would go with any one of the single cylinder four stroke like the saito 100 or os 91. My TF AT-6 Texan fly great on a Magnum 91.