I think the only way to protect more of the psuedo-stem is to simply plant the corm deeper. This was planted about 1ft deep, maybe more, and over 1ft of it survived after a winter low of -9F which is the coldest temperature so far this century here. It seems like having it planted deeper ensures corm survival a bit better.
I have some ensete on order which I might let grow out a little and then plant them 2ft deep just to ensure their survival. I mix in a lot of loose material such as leaves/ peat moss, and organic material just so the plant doesn't suffocate, but it is nice to plant them well below soil lvl just to make sure they survive the brutal winter, and the additional protection is only to help more of the psuedo-stem survive so it has a running start onto the season.