I won't be able to tilt it or remove the door. Final measurements show I will have 1" clearance above the safe (after building up the floor) and 1" clearance on the width. It's a snug fit! That is why I am worried about sliding it.
I cant take the door off because I don't think there is enough room to put the door back on. It won't open all the way once in place. I assume it must be at least open 90 degrees to get back on the hinges.
Good argument against drywall, I might stick with wood and a water barrier of some sort.
I think my current plan for sliding is to put down some white board and lube with graphite. That should make it pretty darn slippery and can be left under it.