I'm curious what the D model is? I just bought my first performance boat and considered some type of lift. (past cruisers were bottom painted) Our dock is in a tidal river with a fairly strong current. Do you need pilings on both sides of the unit? Would it hold up attached to the side/end of the dock in that current. I have a Formula 312 loaded weighs 9,500+/-. Is it rated for that much weight? Price?