With all due respect Fokker the first thing any decent Expert rider would do (let alone Pro) would be to get the bike sprung properly. Once you have the correct springs in you go from there. If you're say 5 stone too heavy for the spring setting (I'm not saying you are watto by the way!!) then no amount of re-valving will give you as plush a feel as you could have with the right springs.
All I was stating in the above was don't automatically assume re-valving is your best option. Getting stiffer springs may prove to be a wiser investment, but it may not. I'd advocate what Fokker says and give someone like Stu a call and explain your problem, as he'll know what best to advise. It might well be a case of re-valving OR stiffer springs, but he'll be much better placed to advise on this I think.
Good luck
