Hi Graham,
Thanks for your response. On Saturday I made an interesting discovery. I swapped the jib sheets to use the inner pair (normally used for the lazy jacks halliard, and topping lift). They held perfectly. I noticed the jaws on the outer pair were not as sharp -surprising if they have worn as the boat has only had light use for two seasons. I'll use this pair for the rest of the year and see how they wear.
Regards
Rod