Looks good, I just painted the inside and out on mine with epoxy paint, but I have an aluminum pan that the mill sits in, so I had to caulk the whole thing.
Are you going to use a pan or liner of some sort ?
Are you planning on leaving that thing on the casters?
If so I would try to find a way to attach the enclosure to the wall or something. My buddies X3 walks his table across the floor!