I'm actually not 100% sure all of mine are RBI hides, now you mention the door. I have 2 pairs of small hides and one set has distinctly taller/larger doors than the other. They look the same size otherwise. The smaller doors are a lot shorter and would probably be more problematic for getting in very quickly, so I see you point there, Calm.
He seems pretty settled, but we bumped up his tub size about 2 or 3 weeks ago and are swapping over to rats, so better safe than sorry right now. His new tub probably has space to add the mediums as well temporarily, so I'll give that a go.
He's funny about how he ends up out from under the hides and with how squishy the parts he pushes out are, I couldn't think of a more accurate word than "ooze". He always seems to flatten out a lot; akin to a cat being fluid enough to fit into weird shaped boxes. That picture above, the part sticking out is nearly half as tall as when he's just cruising around, so it's pretty funny to see.
He seems to like balling up with his head near the entrance and will poke his nose or his whole head out after I've walked into the room to check out what I'm doing. (Probably hoping for food... I think he would be more than willing to take a 2nd mouse if it was offered)
Here's shots of the 2 different door sizes for reference.
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