I increased preload 3 times and on the last time I was at 2.5" front and 1.5" rear. I liked where it was as far as ride height, but it was like 95% compressed at the top of coils and it rode so much worse. We generally carry two large coolers plus tools, etc. which is why I went with 300 lbs springs on the back. With the new coils, I only had time to guesstimate the preload when I first installed them and I've lost about 5/8-3/4" height, but it rides so much better. I'm sure I could increase preload to gain that back without hurting ride quality.
I don't think anything is going to completely remove the top heavy feel, but getting rid of the dual rate springs is a big improvement. I'm also running 1" spacers on the front and 2" on the back which makes it feel more stable.