I too would like to buy an extended swim platform for my 310 FV but have not found any good resource. Have you had any luck?
I haven't yet, swimplatform.com is the only one that already has a mold for the 280, I have spoke with 4 companies total but the other 3 want me to make a pattern which i am not comfortable with. The down side to swimplatform.com is they rate their platform to hold 600 LBS. I could easily see having close to having 1K lbs on it, when we tie up whoever has the larger platforms usually draw the crowds. My buddy has had 14 people on his platform before.