My Continental came with 2x6 extra long bunks. We had to cut about 2 feet off the ends that were extending way out from the aft end of the boat. Even now I still have about a foot extending back from the stern. My boat's weight rests on the keel rollers and the bunks are there mostly to provide lateral support. I think 2x4 bunks should be enough for this job since our Seafaris aren't that heavy.
