: That is a 4" travel. Wouldn't any significant thigh braces would be out
: of position with this much travel?

What really limits the amount of travel available to move the seat is the length of the cockpit cutout. The thigh pads (as well as the backrest) would have to move with the seat, nothing new if you look at the highly praised Joe Greenley seats at Redfish Kayaks. Ideally the foot braces should also move with the seat. Moving knee hooks would be a chalange but I think they could be contoured to remain stationary and still allow several knee positions.