aluminum plate screwed down?
Thick magnetic sheet?
I would keep the vent there and use it to blow cool air into the cockpit though. Its hot when ya race!
I gots two o' these just to blow air..
http://www.boatersworld.com/webapp/wcs/stores/servlet/ProductDisplay?storeId=10051&catalogId=10051&langId=-1&productId=358879
just toss the stock fan.
-Rich