ymfb,
this thread reads quite funny.
You asked for advice and then totally ignored it
pretty much 99% of my riding on the ST4S is two up with luggage, on one trip or another.
I've tried almost evert tyre going now, with the exception of the one your about to fit.
My choice would be either a Pirelli Diablo, or a Conti Road Attack.
These two give me the most tyre life, with a confidence inspiring level of grip.
I really like Michelin Pilot Powers, but they just don't last when 2 up.
Let us know how you get on.
Btw, round and black on ebay do sets of tyres at prices my local shops can't even buy them at. Even when charged for fitting they still work out cheaper.