To make the system safer, they install a Ultra-Safe rope grab (www.ultrasafeusa.com/pdfs/US-5000%20manual.pdf) on the hauling lines and anchor it to the locking rail with a SpanSet type roundsling (www.spanset-usa.com/lifting-steeltex.cfm) and an Omega Pacific HMS Jake 3-Stage Lock-action Carabiner (www.omegapac.com/itemdetail.php?id=59&secid=25). They chose the Ultra-Safe US-5000 rope grab because it is designed to fit over the hauling line ropes (it will fit up to 3/4" diameter ropes).
When a rope lock is released (or slips!) the rope grab will hold the line until the line set is restored to a balanced condition. Flexible, easy to move around, and simple to train the users on.