I, too, race open expert or Open senior (depending upon the event) and run 5.4 rear and .43 front. I use 5 wt fork oil, and 10 wt suspension fluid in the rear with 160 lbs of nitrogen. Acme performed the suspension mods, and she rides like a dream.
On the sag, both the static and race sag are important measures. Set the static at close to 1 inch (.75 is fine), and then check your race sag. If you vary much from 4 inches, you have the wrong spring for your weight (as a general rule).
However, it must be noted that the position you are in while checking your race sag MUST BE your standard position at race speed. Most folks tend to stand with their weight more to the back of the bike, which will change your spring requirements relative to someone else of the same weight and speed but with a riding position more to the front. The correct position has been discussed here at length, but can certainly be reviewed if desired.
Good luck with the suspension setup. I, too, believe the suspension is a critical part of the bikes safety.
Rick