Old as Dirt!
The advantage of cotter rings is that they can be removed quickly and easily and generally without a tool in the event that one needs to drop the life-lines in a hurry (perhaps when recovering a MOB). The disadvantages are those your rigger pointed out, and the possibility of the rings working themselves off and allowing the pins to loosen or drop out, invariably at the worst of times. In my view, however, the pins you refer to are not a good solution to that problem as one needs an Allen wrench, and may need a pliers, to free them, both of which one might have difficulty coming up with quickly extremis. The Jurgan pins eliminate the need for tools but at rather an extraordinary cost per pin. An alternate solution is simply a couple of wraps of rigging tape that cover the cotter ring. It may need replacement every year or so, but then one needs to inspect the fitting anyway at least that often, no? And, the stuff can easily and quickly be pulled loose to access the ring when necessary.A local rigger helped me splice up my dyneema lifelines last week. While on the boat he noticed my cotter rings in my lifelines and mentioned that I could replace them with "a barrel like pin that is hollow and can be secured from the bottom with an insert that goes up and into the pin." The idea was that the cotter rings could be eliminated.....stopping the potential for snagged lines, sheets, and sails. He is off for the cup, and will be hanging around for a return delivery....might be gone awhile. Can anyone name these "pins" or supply a link? Thanks!