Thought I'd share how I attached a downrigger to my Hobie Adventure Island - to the right rear aka. No holes! check out the pics at:
http://s317.photobucket.com/albums/mm389/fishman-rd/It's mounted to a piece of decking board - see the white board in the pics, it's very light. Made the board longer for support, and the extra surface area makes for a good place to set the cannonball...
Downrigger is a Scotty 1060 Depthking Manual Downrigger W/Rod Holder, but removed the Rod Holder. Mounted on a No. 1026 Pedestal Swivel Mount - the swivel mount is a must have! Weight is a Cannon 4lb Flash Weight attached to a Scotty 370 Trolling Snubber w/Snap & SAMPO Swivel
The setup works perfect.. Now, time to Fish on!