Question for you engine gurus...

I am scratch building a 10 ft Lavochkin LA-7 and the spinner is 7.25" in diameter. With a spinner that large, I figure less prop is cutting through the air, thus less load on the engine...? Am I right? If so, can I go a little larger in prop size to compensate for the spinner??

This is very important because the cowl is 15" in diameter and I want to maximize thrust for a plane predicted to be ~80 lbs in weight...

Any input is greatly appreciated...!