Jim, the plane might be big, but it's light. Trainers are designed to have a lot of lift (the wing probably looks very big to you). With all of that lift, it takes less power for the plane to fly. A good, ball-bearing .46-.52 should be more than enough power for the plane. A .61 will be considerably heavier, which might give you some balancing issues, and raise the overall weight of the plane, which is something you want to try to avoid in a trainer. Sometimes over-powering a plane is definitely a good idea, but I have yet to see a .40-sized trainer that needed to be overpowered.