I have tried a similar rig to tow my kevlar carbon Bell Northwind canoe (50 lbs). Even that light, I would not try towing the distances the OP mentions. Also, If you want to attach at the dropout rather than the seat post you have to radically alter how you connect to the canoe, probably by going all the way back to the trailer. The depth of the canoe stem dictates a high attachment point. You can only bolt things to the deck and gunnels of canoes.