Looks like your heading in the right direction. I almost bought that tower! Make sure you measure and have someone else re-measure for concurence. It's hard to find a good reference point on these boats cause they're so round, not many body lines. I measured from the rub rail on the height and thats no problem. The length measurement is the problem. I went from the center of the bow.
Anyway, yes, 1/2" treated ply with liquid nail is what I used. You should have it pretty easy since you only have 2 mounts in the back. I cut my pieces 4"x 12" and they fit fine. I drilled my holes in the hull and in the backing plates. Then I put on the liquid nail on the backing plate, ran the bolts through and snugged them, and let it set up. After it was set up I put the sides of the tower on. Mine had hard, curved rubber spacers for between the tower and the hull. I put the bolt through the hull and backing plate, and put the aluminum 2" round washer, then the lock-nut.
Make sure you have at least one other person, 2 more if you can. The more hands to help hold stuff the better. It took me and a friend a full Saturday to do it and clean up the boat after. Hit me up if you have anymore questions!