Re: Tubing at the lake.
Yes the air seat will fit your FC4. The only difference between the FC4 and the FC4 Deluxe is the air seat and color. So basicaly you are upgrading to a deluxe.
I don't have a FC4 but I've heard about the water getting in the front. My guess is the holes are there so it doesn't retain water. The area was never really designed for a storage area but that's what people use it for. I'm surprised no one has made a water proof storage bag to sell that fit that triangular area.