I don't really understand what you're trying to say stampede; unless you are referring to the line that runs through the 2:1, 3:1, or 4:1 purchase system on the shackle that attaches to the jib. If the jib traveler car line breaks, the jib traveler car just gets sent to the end of the track, solving nothing as far as releasing the jib. If your traveler car races off the traveler, you're still out the new car at the very least. Solution is to blow the jib if you can (upwind) and spread your arms and legs prior to impact with sails (I know, easier said than done).

The Infusions run a cleat to the base of the spinnaker pole, slightly easier on an aluminum pole than a carbon one. Make sure your pole doesn't twist or your traveler car will be at different positions depending on the tack. The holt-allen and I believe the new Harken self-tacker have spring-loaded adjustable end stop points fitted to the traveler itself, which is nice on the F18 but probably less used on the N20. They've also gone to a double Harken 16mm block on the traveler, for ~4:1 purchase on the jib; the newer sail cuts need to be cranked in tight to aide in pointing upwind.