The battery is already as far back as it can go. This is a pretty small plane. The 11 x 5 prop will be spinning in the water or chewing spray. I am a firm believer in power like everyone else but this situation creates limits to weight and prop selection. If you lay a straight edge on top of the floats the end of the prop is very close to it. With the 35 they sat pretty low in the water. With the 45 they will sit even lower. I may have to change the mounts for the floats to get more clearance. Everything you do like that makes it heavier and it is already a small plane with big floats. The way the floats are mounted limits how much they can be lowered to gain clearance. I will keep playing with it until I turn it into a flyable airplane or make it a submarine. Will keep you posted as to what I find.