How much internal air flow is enough to keep things cool?? I am currently building a .40 size pattern airplane and converting it to electric from glow; Due to the design of older styles of pattern aircraft, the nose and fuslage are pretty narrow, and the firewall was designed without cooling holes (solid). I realize that I've got to design and construct airways thru the fuslage to keep things cool. Your opinions, please, on just how many square inches of openings for both the cowl and fuslage are gonna' be necessary for adequate cooling???? Is there a rule of thumb???