is this what your lookin for PAPPA? http://www.castlecraft.com/canoe_stabilizer.htm
the prisce is high but if you git a idea to make them, i would think a heavy gauge pvc, or light metal would work to attach some type of floats to um...? lots of good add on & ideas on that site, i want the sail kit but i'm scared i could git to the back of the lake but not return...i need a sail class or somethin`first...
try usin 3inch or bigger round pvc 2-3 feet long or longer with caps on the ends as your floats and cut them in half to atach a pvc T to the middles ,but down size the T fitting, 3" on both sides of the T and maybe a 1 inch on the on the one side, or you can slowly make the pvc smaller with down sized cupplers.... you need a pvc primer & glue, but you could also fill the void in the middle of the pvc with expanding foam... it sounds confusing in writing but it should be easy....