Does it still feel like you are about to fall over backwards and it's the boots/skis holding you up or did you find that the squat is easier because your COM is further forward?
getting your shins/boots a little more upright might help you here. (not squat deeper) but ski better balanced.
If you push your knees back just a little (remove the spoiler from your boots) I bet you could ski stronger and better balanced.
In that second image, if you look where your knees are in comparison to your feet you will notice that the knee is just out in front of your toes. In order to be balanced over the arch of your foot in this image with your shins slightly flexing the boot, you can draw a line straight down from your hip socket (I'm taking a guess looking at the picture) and the line would be somewhere behind your arch, between your arch and heel.
If you raise your toes (try shimming under the toe piece of your boot) with 2 layers of cardboard (like a cereal box top) to get about 2-3mm of lift and try again.
Or remove that spoiler (similar affect) I bet your knees would move back a little and you would stand taller. This would put your hip socket right over the center of your boot..
Since that image is in photobucket, I can't edit and draw on the image. (well I could if I had time to do a screen capture, save and edit) but I need to leave the house real soon.