Thanks all for the replies. I think I understand the nature of preload now. Essentially the spring rate is linear, so changing preload doesn't make it harder or softer, simply changes the ride height to counteract rider weight and therefore determine sag. A heavier rider needs more preload, as without it they will compress the shock "lower" more when sitting on the bike so they have too much sag. A lighter rider needs less preload, so the bike rides lower, and their lower weight presses the bike down less.
The only way to make it "stiffer" or "softer" is with a different spring, and the only way to improve the quality of the ride is with a more expensive shock and/or with better/adjustable damping (or a softer seat?!).
Is all that right? If so my only last question is what setting of preload should I run it at at a guess (I will try measuring it, but at ballpark what do you think?). Currently it is on minimum preload, and stock it was two clicks of pre-load.
Thanks for all the helpful info and advice
