Spare halyard--what's the best line?

[JohnV]

It's very tempting, and undoubtedly would be a very satisfactory system. But to stay with your earlier points about cost/benefit, I'd be springing for 90-odd freet of Dyneema, in a size thick enough to grip, as a seldom-used spare, but using sta-set x with its relative stretch for the main halyard. I'd want to swap, and then I'd be back to having a fat, heavy dacron line as a spare, which I'm trying to avoid in the first place.
And 2 times 90 feet is costly and hard to justify on a heavy cruising boat. Especially when Mr. genoa halyard starts to get jealous.
And as I think about it, I'll still have the 3/8" spinnaker and staysail halyards, so maybe just a thin, cheap messenger is really the way to go.
Thanks for your ideas.
John