Thanks gents
FWIW, the main reason for looking at the longer tubes would be to get back some of the free length I apparently lost with the (96-97) 900RR forks. I had read that the (900RR) forks used on the Moriwaki race bikes used longer tubes (I would imagine to get them back to "stock" length).
As for the why behind all of this, I found the bike gets a touch nervous when the speeds get up there (like over 100 mph, I very seldom get there as I can't afford to lose my licence, but it happens from time to time that I do a run through the gears). I will try to drop the rear (am currently running a 4.1mm shim on the shock but will either remove it or use a thinner one) to see if that cures it. I thought longer tubes would be a way to get the length back to stock (would have to get a spacer for the spring, 42mm should do the trick as it's the exact length difference from the 900RR to ST tubes).
Incidentally, I recall reading that the linkage essentially multiplies the gain in ride height (compared to shim height) by a factor of 4. Can anyone confirm this?
cheers
99 VTR1000F Firestorm, a.k.a. The Carbon Express