i use the bolt in curved ones like ST's 3rd link. i love them. i use an aluminum canoe with all sorts of stuff (rods/tackle trays/paddles/fire grate) velcroed up into it. fully loaded it probably is something around 75-80lbs, maybe more. i have no issue taking the canoe and my pack and single portaging everything.

i made a couple yokes using 1.5" conduit pipe and closed cell foam. i couldnt bend it how i wanted so i ended up cutting the pipe for the curves and JB weld and duct tape to keep the joints strong. both yokes failed after 3 trips and having to rig a yoke out of rope is no fun. im sure a trip to a car exhaust shop using exhaust pipe and their bender would have made a yoke that lasted longer...