For for this application I'll need about 45 feet of Dynex Dux in 3/8" diameter to replace 6mm 1x9.

In my next project (probably not until summer) I'll need about 115 feet (finished size) plus enough extra to make 4 splices, to replace 8mm stainless backstays. I figure ~3 feet per splice so let's call it 130 feet total. I don't know the proper diameter to use -- 3/8 will provide enough strength but I'm thinking 7/16th Amsteel Blue, to up-size enough to allow for 50% UV degradation over an estimated 5-year replacement cycle (at 40-degrees north latitude). No need for Dux in this application because these are adjustable backstays. Will also need 8 stainless thimbles and some appropriate sized D shackles.