I'm sold on the cheapest HMPE, which so far is D97 (though all I have so far is brown D10... foolishly spent extra for barely better), all the different ones I've seen in that web store are significantly more expensive and I don't buy that they're too much better, though I haven't tried them. The composite vectran/HMPE materials are apparently a little bit 'better performing' (so harder on the bow?) but also less durable, or at least more prone to fray.
Some people say the difference between dacron and D97 equals the difference between D97 and BCY-X or whatever. wat. I so don't believe this.
For Dacron I think you'd have to make a thick string with as little twisting as possible (without allowing for ballooning).
why not ask Joe Gibbs about his super thin hemp string in his 180lb bow, if I remember right.. O_o