I'll pop it on the bike sometime and measure exactly how much it raises the rear end and take it from there. Interestingly the factory low option rear shock is 375mm long, just about perfect for a Rockster I would guess....no good on its own as spring rate (and doubtless damping) is too soft.
Aim is to raise the bike about 2 inches both ends and soften the spring rate slightly as some of the back roads we go on can get a bit exciting. That amount of extra length will then allow me to tuck the centre stand away properly and I'll have my ground clearance back again.

Not sure what to do with the front yet, I've got a cheap GS Adventure shock just to tryout and see how much it raises the front. Much of the extra GS travel seems to come from different wishbone and forks....not just the shock itself unlike the rear. Will probably have to go new, although Nitron is a slightly cheaper option with the very useful feature of having spring preload adjustment on the bottom of the unit where it's easy to get too. Brake lines will doubtless need replacing as well which is a pain as the Rockster has decent braided ones as standard.