So while I wait for the ice to clear off the rivers up here (though it looks like Robert was out up in Edmonton already). I figured I would finally solve the directional stability problems I have been having with a transporting a 16' boat on a car with narrow cross bar separation.
Found a couple J-cradles at a surplus store for 23 bucks, and ended up removing the rivets and cheap plastic bits that came with them and bolted them to a pair of 5' steel pipes, ala Mr. Yost's extension rack.
To make it relatively quick to remove, I put a wingnut on each hold down and notched the lower plate, allowing it to swing out of the way. Only takes a minute or so to toss it on the cross bars.
Its a lot more stable on top now, no side to side movement at all.