I did not put a hole in the rear bench for the seat mount. Instead of using the aluminum tubing on the rear, I used 2x4's to make the frame and then added another 1x4 to build it up. The rear deck is not screwed down and I made it to actually fit across the center side benches of the boat as well. I did this so if I am fishing by myself, I can sit in the center of the boat and pull the seat out of the bow to stand up there. That bench is extremely stable and will not tip. The decks actually straddle the aluminum boat bench supports to keep it from sliding front or back. When traveling across the lake using the Johnson outboard, the pedestals for the seats are removed and the seats put into the bases in the floor to lower my center of gravity. I'll post some pics of the underside of the rear bench soon but now I have the boat under a tarp.