I assume you need more calf room? If so, you can flair the cuff in the back. There are ways to do this. Let me see if I can find a video.
This is a pretty old post. Is stretching the cuff one of the better methods to fix this?
My quads are always burning in my Technica Mach1 120 MV boots. Not so with my K2 Mindbenders, but I love my Technicas and would like to keep them and have them be my primary boots. The K2s are very soft and have a pretty wide cuff all the way through the ankle area.
The #1 suspicion I have is that the tight cuff fit around the calf puts me too far forward and I also don't have the benefit of a restoring force coming out of a turn.
I have 18+ inch calves (had them my while life seven when I was 155lbs in high school)
I'm heading to see a bootfitter today about it and wanted to get a little educated on it.