Brandon, this would be easy except for the extra 100lbs of gear. You are basically looking for the displacement of a small double. I figured 65lbs for the kayak since any kayak big enough for you and 200lbs of gear is going to be a big boat, and a big boat with that much gear will probably need to be built quite sturdy. Your choices can go the proportions of a conventional sea kayak but that leaves you with paddling a 20ft+ kayak, something Ned Gillete did in a necky tofino for his famous paddle to Hawaii. Or go the route of something similar to the dimensions of a folbot, 17ftx30in or so. So what kind of water are you going on? One possible no brainer option is to get the plans for a Ches.18 and add about 3/4" to the side panel dimensions. What kind of handling are you looking for? Straight line efficiency, manueverability. So don't deny us a good laugh ,, what do you paddle in white water?