I had been conflicted about whether to put an adjustable backstay on my masthead rigged boat, and couldn't find much info on the net that wasn't as conflicted as I was. Therefore I'm posting this in case anyone else has the same idea. The idea was that it wouldn't do much to flatten the main on a masthead rigged boat, and might mess with the lowers (I have fore and aft lowers). Well I went for it anyway. It actually costed less to make a new synthetic backstay than to hire a rigger to swage an eye on the existing one (amsteel is getting cheaper and cheaper). So I spliced it myself using youtube instruction (piece of cake) and installed it. Put in a fiddle block and two cascades to give 16/1. Whole set up costed about $150.
Yesterday I went out in the rain and tried it out. Wind was very gusty, going from about 6 knots to 15. I torqued the backstay in the gusts, let it out in the lulls, and found it to be very effective. Maybe not quite as effective as on a frac rig, since it doesn't flatten the main at all, but still well worth the effort. And I haven't ripped out the lowers yet