I have been spearing for about 8 years now and have made 4 shantys and the first one only lasted 2 years cause I didn't like how I made it but my last 2 were built good. Here are some tips........
1. 56" is plenty for 2 guys
2. 6ft is max
3.go with a bigger hole, more like 3' by 3' or 28" by 46"
4.a flat bottom is best so that ice cant freeze in any cavity's
5.a slant roof will help drainage
6.use anchors
7.you might want to use 2 by 3's for the floor framing because the water really gets to the floor when you keep heating it up and then it freezes
8.Hunting steps work great for handles on the out side of your shanty
9.give your door a extra gap for ice build up as well as contracting and expanding
9. make it as lite as you possibly can for a few reasons, one is that you will need to pick it up to get 4 by 4's under it and then even with a snow mobile you have to think of slush and or no snow on the ice and also thickness of the ice as well as a heavy shanty will make ice under 10" sag and can flood a shanty if not moved or propped up again
I'm sure I'm forgetting allot
but I hope that helps