Slicks aren't always the grippiest way to go unless you're UBER fast. Road legal, treaded race tyres like Metzeler Racetecs for example get warm quicker and stay warm easier because of the extra surface movement (and subsequent heat generated by internal friction) allowed by the grooves of the tread pattern. It is for this reason that many racers cut their own grooves into their slicks with a special tool to combat cooler track surface temperatures like what you'd get in spring, autumn or in England.

I'm pretty sure Racetecs come in a 150 section rear and 110 section front and they certainly don't lack grip - i'm considering a set of these myself. My only worry is that tyres like that are designed for use on 600s and the like which are much heavier than an NSR (particularly a stripped down race version) and therefore won't work as well as they might on a 190+kg machine.
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