Had an idea...
How would it sail now that the center of effort has been moved aft? For your canoe, you could get away with a single leeboard, but the crossmember should be made of metal. The crossmember should be shaped like an "L", with the bottom about the size of a postcard, and, if aluminum, ⅜" thick. Its two-clamp placement would be about one foot aft of the mast. I'll send a picture of the shape I'd copied from Grumman, but re-made and enlarged in ½" marine plywood. Those original parts were sold to a chap in Maine, who wanted sail-power for his Folbot kayak—Of which, I have two.
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It's 31-inches from bottom to the point of attachment. (The original had a 4-inch handle which made it unnecessarily longerGreat! WHat's the length, I was thinking a Shadow or Barrington board may work, although we are going to try adding a mizzen first...to the canoe.
Sea Trials! CHIP did awesome, 14-17 mph winds and a lot of chop on the bay. We shipped a lot of water into the cockpit. The rig held up great, she felt very stable and the sail set beautifully.