I will chime in a little bit. I lost 50 pounds so that I could learn to snowboard back in 2010 and I skied a few years prior to losing weight and I had a hell of a time finding ski boots to fit - I have HUGE calves also - always have and still do. I finally found ONE pair of ski boots that I could actually wear but my husband modified them to fit me to my liking. It got me to learn to ski, somewhat, but I just could never progress past the blue runs on skis so I tried snowboarding in 2010 with my goal to lose 50 pounds and turn 50 all in the same year AND try to learn to snowboard. Even with my large calves my hard part was my size 6 1/2 EEE (triple E wide feet). Finally two weeks ago tried some Ride Sash Boa boots and they are wide enough and fit great. They fit my calves, but in your case, I would say do whatever you feel you need to do or modify them to work for you. FYI I also worried about how to get up from the sitting position on a snowboard as I have very week knees and not nimble like the old days. My husband rigged me up up a "handle" attached to one of my bindings and I pull on the hand and can stand up that way. I can roll over and stand up on my toe edge now, but when I was learning it was hard for me to start on my toe edge and to turn to heelside - this handle thing really help me. If you want to watch my learning to snowboard and laugh at my falls, here you go!
Wishing you luck and have fun!!