I thought about it some more and checked it out on my windward sheeting rig. when the main is loaded by wind force the leeward camcleat should become unlatched . This allows the windward cleat to be released and the traveller then can be moved up or down. Like I said earlier ... in a tack or gybe the traveler sometimes goes over the leeward traveler sheet jambing it all up. The car must be moved up to get the line out from under the traveller car. I too considered a continuous line but will I be able to reach it from the rail or should I add shock cord somewhere to make it work?
good luck,
clint