Here in the midwest almost everybody who lives on a lake has pound in pier posts for their piers. These would be ideal for you ramp. You simply make the pier/ramp as wide as you like with the pound in posts (later you will cut them so they are below the siderails and stringers), make it long enough to get you past the rocks(you can even slope the ramp to below water level with the pound in post system), then cover it with plywood or OSB (be sure to add enough stringers to give it some strength down the middle)l. Then cover the whole shebang (at least where the hulls will touch) with indoor/outdoor carpet. When you are ready to launch simply throw a couple of buckets of water to "grease" the ramp. Best of all you can lauch or retrieve your boat by using a simple boat trailer winch (you run it from below to lauch...above the water to retrieve---for me it is pretty easy to push the boat into the water...and it is really nice to be able to quickly pull the boat out of the water and above the waves). Wondering what to do with the pound posts at the end of the season? Go to a junkyard and get a truck style 3 legged jack. Attach a lenght of chain to one post at a time....jack up to apply pressure...then tap the pipe with a maul to help free it. Once it starts to move you can just jack it out of the ground/water.

Best of all, if you label the pipes you can use them again next year in the same location they came from (instead of pounding on the top of the now cut off posts....you put a wooden block on top and pound it in by hitting the block...not the much softer pipe head.

Hope this idea helps!

Paul
Milwaukee, WI