When my Atomics were failing me, I had an assessment done. The bootfitter said that boot was not the best for me, but he could make it work. I skied them for a few more weeks, then replaced them.
I wrote notes from that assessment. You could do some of these things at home to gather some data. And I know you like gathering data on this! To reiterate for others -- this is data gathering ... not diagnosing, not prescribing solutions, and certainly not replacing the knowledge of an expert bootfitter.
Stand in sock feet, facing a long mirror. Probably best to be on a hard, flat surface. Assume a skiing stance. Maybe notice how each of your knees track as you bend them. Do they move to the inside or outside?
Put on your boots and buckle them just as you would for skiing. Assume a skiing stance.
I think the first thing he checked was the effect of adding a thin shim under my toes (a gas pedal). I was equally balanced (or unbalanced) with or without them, so there was no benefit to be derived by them. He removed the shim.
In your buckled boots, assume a skiing stance. How do you knees track? Did they move inside or outside? Move your legs to the left and then to the right as if edging skis. You might need something to hang onto or support yourself with as you do this, especially if you're on a hard surface. [The bootfitter told me I was not forward enough and that I drop my hip when I emulate edging. No idea how to describe what he was seeing. But when he held up a full length mirror to show me, what I saw was that my legs were not aligned, one to the other. They were all over each other. I thought I looked like a kid who had to pee.]
Unbuckle the boots – completely unbuckled, not just loosened. Assume ski stance. Emulate edging. [For me, this was totally different. I was more solid on my feet. I was far enough forward. And the edging motions didn't make me feel like my legs were fighting anything, including each other. This difference between buckled and loose boots indicated to the bootfitter that the forward lean of my boots was wrong.]
Having a better stance and being able to move better with loose rather than buckled boots led me to ask whether my boots were too stiff. The bootfitter said no, that I was already laying on the tongues; ski boots are supposed to fit without even being buckled; buckling provides an extra layer of support; boots should not feel totally different between being buckled and unbuckled.
I cannot explain why too little forward lean caused me to drop my hip or caused my legs to not be aligned with each other when emulating edging. I do wonder how much extra stress that puts on muscles, joints, and ligaments when skiing and how much more injury-prone that would make a skier.
Then, add the spoilers and/or other material to your boots to increase the forward lean, buckle the boots as you would for skiing, and try the movements again. Do your knees track differently? Better or worse? When doing edging movements, are your legs aligned better or worse? Do you feel more stable or balanced, or less so? Is it easier or harder to get into a proper forward ski stance?
You can try the same things with some type of shim as a heel lift or thin materials to lift the toes (gas pedals).
@MissySki, you posted previously that you have some significant A-framing when you ski and that you were planning to have that addressed with your next boots. If you do the tests my bootfitter had me try, you might pay attention to left vs. right leg, compare whether there are differences in your alignment in the old boots (buckled, unbuckled) vs. new boots (buckled, unbuckled), and no boots. And make notes to take to the bootfitter when you go back. You might also take with you the materials you used as spoilers/shims so they can see the thickness. You might even take photos as you go and sit back later and look at some of those side by side to more objectively see what effect each change had.
Your bootfitter may perform different kinds of tests from what my bootfitter did. But gathering data may give them a starting point. It gives you points for discussion and better understanding of what they're doing. And may give you more confidence in whatever changes are eventually made.
Also, if you were A-framing before and the boots are fitted in a way that reduces or eliminates that, things will feel different and it may take you a little time for that to feel natural. Whatever changes are made -- whether by your testing out some things on the hill that felt better at home or by your bootfitter as they dial in the fitting -- ski some easier runs at first and pay attention to how your boots and skis feel. My bootfitter made the shims and gave them to me to test out on the mountain (no shims, thick shim only, both thick and thin together) before installing them permanently in my boots. I spent several hours on the hill experimenting with the shims on different runs, then had my instructor install the shims so I was kind of blind testing them and he was assessing the impact they had on my skiing.
