I attach mine using a couple of cable ties to the straps at the rear of the seat. The trick is to position the cushion so that the bones of your a**se get behind it and you will not slip forward, correctly attached I can fish all day and not need to reposition the cushion. As for feeling any higher, I think the difference is minimal. I leave mine permanently attahed and inflated but don't fish remote waters therefore never have to consider the amount of gear I carry.
Matty