RE: Engine mounting
The side mount may change the lateral balance some, but don't let that deter you from side mounting. You will likely have more of a weight difference from other things, like heavy wood or more glue on one wing. I always laterally balance my planes. Even if you are only a sport pilot, a plane that is not laterally balanced can give inconsistant performance. Especially in a loop, it will tend to pull to the heavy wing side.