Rmk, your saying you have more static sag with a stiffer spring? Opposit of what I would have thought, I'm about your size 185-190, I had sag set at 100 because I read that somewhere that's what worked best on the 450f, couldn't find anything on the fx. The bike works great in sand whoops but a bit stiff in rocks & roots, lowering in would be helpful in the technical, I'm 6' and am on my toes on flat ground.
Before I did this, I asked the same question. I figured if you went to a stiffer spring it would make the static sag less and it would push the rear end even more up. I was told by many that is not the case, because you take out the pre-load and when you sit on the bike its plush and not that pre-load harshness. They were all right, when I put in a stiffer spring, I don't have that preload and the bike dropped. I would definitely consider putting in the 5.8 if your around my weight and drop those forks 4mm. ... When you sit your sag to 100, what was your static sag? If your less then 20mm, I would go the the next stiffer spring. The bike felt so much better.