I ran an RCV 90sp in a Hawker Hurricane, whichwas quite a tightly cowled installation. I had a small'ish intake under the chin just behind the spinner, around 1" square, with a baffle directing the air up toward the engine. But as stated the header and exhaust get in the way and the baffle had to be cut around the header pipe. I had an opening at the back of the cowl at the bottom easily three times that of the inlet, and I still suffered bad over heating problems with the engine smoking &hissingquite bqdly after landing (ran on a totally synthetic fuel) I finally got it to run without too much over heating by cutting the small rim that wasleft on thefront flat face off the cowl behind the spinner leaving a clear gap (only a few mm) around the cowl and spinner looking from the front. Not overly obvious, but it made a hell of a lot of difference in allowing air to flow directly over the engine from the front. I know everyone says the fins on the SP's go the wrong way, but with a fairly close fitting cowl getting air directly in from the front seems to work.

Walts.