Thanx for the help,I started this hobby years ago(and I mean years) in control line and then on up.It still gets a little cofusing,I was sitting here looking at the planes I have,being the GP Tiger Moth,LT-40 and the 4*60 and they are all pretty much the same size heck the wings between the * and LT look like they can be switched. so how is engine size rerally figured out? short answer will work haha