Originally Posted by Pleiades

You may well be better off going for a new shock sprung specifically for your weight, rather than a re-spring of the Sachs unit. It's worth considering that if you've done 15K Km or more the OE damping will be quickly fading away and a new (stiffer) spring will compound this problem, changing the spring is a cheap, short term fix. The added bonus of a new shock, which ever you get, will be that they are all rebuildable and will last you a lifetime.

Don't forget there are other very good (and cheaper) options than Ohlins - Wilbers, Nitron, Yacugar etc. It all depends how much cash you've got to burn!