Thats a class idea! Only thing i can think is that the sliding ring may get hung up on the canoe thwarts and or yoke and cause an interesting issue, but you'd have to do some experimenting to find that out. Me and the mate i mentioned previously are thinking we may head down sometime next week, wetsuit up and have a play, we will try your idea and our idea and see what happens with both when you run the canoe back and forth a bit, basically just see if we can "fix" the current issue (cant possibly make it any worse from what I'm hearing). If anyone wishes to meet us there and join in the fun, I can give you a day and time we'll be aiming for the croesor end of the lake once we've worked out when we're both free?