I'm wondering how much performance difference is there between the .12 and .15 range of engines. I'm talking about Magnun / ASP / Super Custom engines here. They are all basically the same engine and produced in the same factory. What I want to know is how much performance does the extra 0.03 cid give? Will a model designed to fly with a .15 fly with a .12? Most people overpower their models, but I am looking at underpowering. I have a couple of .12 engines, and the LHS has some nice .15 ARFs. The models are Extra/Cap/Edge types.