Instead of butchering up your cowl, consider building an access door to hide all but the exhaust hole. I silver solder a socket head screw to the needle, and access it through the access door with an allen wrench to set the mixture. You can use a remote glow setup and not need a hole for your glow driver, The exhaust holes are best serviced as per the note from Minnflyer. Remember that you need at least 3 times an much cooling exhaust area as intake area.

Bill, AMA 4720
WACO Brotherhood #1