I'm sure you'll get more/better responses, but here are some initial things to consider.
1) Tank position in your cam bands. Too low will get you feet down. You don't mention what kind of tank you are diving, if you are diving longish tanks, this could be a bigger issue. Get your tank high enough in the bands so that your head is touching your first stage when you tilt your head all the way back.
2) Hand position: getting your hands out in front of you helps with balancing things out and will get you more level.
3) Leg position: Having your torso/lets level in the water with your legs bent at the knees will reduce the level length your legs have on your center of gravity, causing you to be more level.
4) Distribution of weight: You mention you are diving a SS backplate. Is that all the weight on your back? If so, moving some weight from your belt to your cambands, say, by using those XS Scuba pockets, can help get more weight closer to your center of gravity, and allow you to get more level in the water.
5) Overall weighting: You've mentioned you have dropped a lot of weight off your belt, have you determined you are properly weighted? I find I end up feet-down when I am generally overweighted, even one or two pounds in the wrong location can do it.
Finally, since this is a combination of both trim and weight amount/placement, take a look at this video on trim, it will at least give you a feeling for what good trim looks like in the water:
http://www.breakthrudiving.com/videos/frogkick.html
(the above is in the context of a particular kick, but you will get the picture in terms of overall trim).
