My GS TF P-47 weighed in at 28lbs with my FG84 and it was adequately powered. Yes the 90 will have more power, however not a HUGE amount more. So anything much over 30lbs I would say that the 90 will not be powerful enough. Depends on aircraft as well, but WWII warbird in that wingspan size are generall over 35lbs, and closer to 40lbs. So Yes I am sure it will fly it, but only with marginal power. 30lbs and under tough and I am sure the 90 will be MORE then sufficient. The Hagar 9 Corsair, or TF corsair, TF Zero, or even FW190 would all be prefect for this engine.