I used 2x2 strips as "legs" for my front platform. I wanted to be able to take the pedestals in and out with ease, so they are removable and not actually attached to the boat. The only things attached to the boat are the following..
1 - 1x2 strip in the front side of the front bench to keep the deck from rising up. I didn't have this problem with the large seat pedestal, but when I put the offset pedestal in there, it made the front rise up a little bit.
1 - 1x2 on the rear middle bench for the deck to rest on. I only put this here as a precautionary measure incase any of my legs broke. Not really needed, but it give me some assurance should the inevitable happen.
Rear deck - This is just sitting on top of the ribs. You can look through my post to see how I have it braced and then the plywood notched to fit around the ribs on the side walls.