I replaced my halyard with 2.8mm spiderline. My wire halyard had a fraying wire and wire halyards aren't exactly state of the art anymore.The 2.8mm has a splicable core, but it is small stuff. The splices actually weren't that bad. Spectra, dynema and those aramids are known for not holding in cleats. The spiderline in a double braid with a polyester cover, it holds in the jam cleat fine. I spliced a halyard to replace the wire and used another length to make the tensioner. The spool of 75' of line cost me somewhere between 15 an 17 dollars, didn't seem price prohibative. I also looked up the breaking or working strength of the 7x7 1/8 inch wire for the stock halyard and it's typically around 450 lbs. The 2.8mm double braid line is rated at 1200lbs.
I'm sure it's not class legal.
Thanks, that was exactly what I was looking for. I was looking at the spyderline too, glad it works. So why do you need the tensioner at all? I always tighten just enough to take the wrinkles out. Do you really need the extra 2:1 purchase you get from the tensioner?