opjose - We're not comparing a ST .61 to a ST .75. It's a Tower .61 he has. The ST .61 as I understand it is a speed motor meant to really strut its stuff at 14-15k rpm. A motor like that stinks for 3D like you're talking about. The Tower .61 isn't know for being such a screamer, which would lead me to believe that it'll fly a 60 size sport/aerobatics plane just fine.