the purpose of the forestay is to keep the mast up until i raise and set the jib. when the jib is up all the load should be on the jib luff wire, otherwise the luff will sag and i will be slow upwind. if i use good quality line (2-3 loops of 1/4" dacron?) and can tie reliable knots- a bowline on one end and three half hitches on the other- then i would be able to sail with confidence that even if the jib wire fails my 3 loops of 1/4" line will keep the mast up until i can return to shore.