If your boots are too wide in the heel area I would look into J-pads or L-pads that you can stick to the inner liner. They come really cheap and helped me a lot with heel lift: 1/8' BOOT FOAM- 10'x10'
Yeah, I just bought a couple sheets of foam and some heel lifts from Tognar. It'll help with these boots until I get better ones, and learning how to modify my boots should serve me well in the future, so I can look at a wider range of boots for specific needs (especially if/when I start getting more into splitboard mountaineering with some of my skier friends and want to go with hard boots). I'll still look for a new pair this year, but hopefully I can make these work for now.