I wont use gas either, I had a ST 3000 in a 25 pound Pica Spitfire. The performance was ok but not great. I had a Moki 180 in a 20 pound Yellow P-47. It had pretty good power but was hard to start as it was inverted. I replaced it with a Saito 2.20 and it is great now. I think if you can turn a 20x8 at 8000 rpm you will be fine. I dont know if the ST 3250 will do it. The 4500 might be a good choice as you might need nose weight anyway.