Well I can tell you that of the few fan's that I've replaced, every single one of them was on a customer's machine-and out of all those, every single customer would have been PISSED if I'd cut a hole in his floor/fender. It would have cost me a fender/floor. I give them the option, and so far not a single one of them has requested the floor hole.
Think about it--later when you go to sell or trade it in, buyer (or dealer?) sees the hole and plug, and potentially is going to deduct that from the offer. You might not know it, but they probably will. Especially dealers.
