+1 on Joe's two posts above! (or is that +2?)
Z5 or FlyLite is aimed at the recreational fly-for-fun pilot... the balance of pro's and con's is much better suited to 90% of hang glider pilots, maybe more. Back-plate-slider harnesses give up a lot, to gain a little... and that trade-off should only be accepted as worth it to the most hardcore of pilots, flying the hottest wings, and doing long, fast glides. The given-up usability (primarily landing ease and margin) is the same regardless of what you fly, but on a Sport 2 or even a U2 (or similar) very few people are flying fast enough for the reduced drag to make any difference worthy of the sacrifices.
And Joe also touched on the concept of dangle-angle... SOOOOO many people out there are flying these so-called race harnesses at a very head-up angle. If you're going to do that, the lines from a conventional harness would be in the wind shadow of your body anyway!!! Aerodynamically, we should be hanging just slightly head down from level- 7 degrees or less I think I calculated it to be. Flying level or even slightly head high, the performance gains of a back-plate-slider harness diminish quickly... but at least you get to keep all the sacrifices
Not to say the Rotor (among others) aren't beautifully crafted and highly functional harnesses- they are! But they're just not the "right" harness for most...
Shut up and fly.