Good advise from Brad, I had a Big Lazy Bee that wouldn't get off the ground with a 46 engine. When I went to a 60 engine the plane was pulling so hard to the left when I throttled up that it was very hard to steer on the ground. I added some right thrust with a few washers between the firewall and the engine mount and that solved my problem. I haven't seen a need for it on my planes that have the 40/46 size engines but maybe that just me. [8D]