[BigBoy2U]

Well I only have my 94 Avion to go by but they used two methods, one was a single hose to heat the basement and a trick used by many was to cap this off and put a few small holes in the flex duct to cut down on the heat put into the basement. Second just the uninsulated duct work gives off enough heat to prevent freezing of the tanks in above 0 temps. Now I dont stay where its more than in the low teens so this might be enough for me.

I did think about the positive pressure of the cabin and the return air flow. Think I am inclinded to make a 1/2" wire mesh cover to go over the blower intake and stick a woven fiber filter material to it. Pull it off to clean and pop it back on. Really a simple bend and fit over the end of the blower. Only the bracket for the board is in the way. To bad they didnt make a slip in filter to cover the blower intake and then they could charge you $10 per filter and make you change it every 3 months....LOL