I have been researching line a lot recently and basically you need something with a dyneema core (perhaps blended, but should be "high tech" core) with low stretch. Some recommend pretty pricey line and I am of the opinion that line that costs 2$ a foot (or even 1.50 a foot) is too expensive provided you know where to look for inexpensive line.
Marlow Excel Racing 4mm (5/32) is what I use on my HT spin halyard and tack line. Its a 20sq M spin and it works fine.
Boat US and APS sell the 4mm for .78 per foot.
http://www.apsltd.com/Tree/d3000/e852.aspBoat US/West Marine had this stuff on sale recently for .39 per foot.
Make sure you get the Racing, Boat US/West Marine also sells the Marlow Excel Pro which has a poly core. You want the dyneema core, and the jacket on the Racing has a yellow fleck,so look for the yellow fleck in the line.
