I just got the 8' X 67-72" Leader Accessories one mentioned by others for my 14' raft this spring so I could do some shake down trips in advance of a Grand Canyon trip this summer. I ended up going with 24" slide rails just so I'd have an easy way to connect the bimini to my frame. Being kind of lazy and not terribly handy or creative, I can just use two hose clamps on either end of each of the slide rails to attach to the boat. Plus I get the advantage of a bit of adjustment fore and aft, but I don't see a need for more than the 24" the way my boat is rigged. I have it mounted in front of the oarlocks, so it only flips forward to close up.
Fwiw, I left it up during some pretty strong winds that played hell with the kitchen tarp during a layover day, and the bimini doesn't budge. The box said something about lowering when exceeding speeds of 45 mph. I generally don't row that fast, so I think I'm safe other than trailering to and from the river.
Show me your OOOOOO face