Well I find on my own, the rear preload is best set to position number 5 (one notch up from standard; bare in mine I gotta counteract a topbox alot fo the time). With maria on the back, I put it up to 6. It makes a marginal differance, and I only do it because I know theoretically its probably a good idea...
Don't know about front preload, as I dont have that adjustment
Matt