Gordon - The R4's don't have nearly as much traction when they're not ballasted, partially because of the wider footprint. With their extra volume over R1's, they do fairly well when ballasted to the same percentage. I'll bet the tires on your loaner aren't ballasted, and are over-inflated. Even so, the tread isn't nearly as aggressive as the R1 tread, which is why I like the Michelin XM27's so much - R4 profile, R1 tread, radial design - if there's a better tire for our purposes, I'd sure like to know what it is.
I'm glad you got a chance to try the HST for yourself. Sure beats taking my word for it. /w3tcompact/icons/wink.gif
Mark