Snells may have adjusted your preload, which won't alter the length of the shock when on the centre stand, but may affect the static sag.
you adjust the ride height using the aluminium link rod. Its a b@stard to get to the bottom end of this, but is well worth adjusting it. Doing so also affects the sag.
I have no doubt that my ST4S handles every bit as good, if not better than both the 996 and 998 I had, and it is miles better than a VFR in all respects (power, turn in, brakes).
Tyres play a big part too in sensitivity and turn in speed.
Do you ride with panniers or a top box ?
Top box if loaded up really can get a weave on, especially if solo with it fitted. Its because the weight is so far back.
I think I ride my bike quite hard (difficult to compare with others I've not ridden with), and its as stable as anything cornering at anything up to 140, solo or fully loaded and 2 up. Let the rear tyre pressure pressure get a little low and it starts to 'porpoise' in the bends.
Oh, and I'm a lardy 16 stone.
Hope thats of some help.
Cheers,
John.