I had our Robo in the Mickey 2XL and thought it was ideal
Personally I wouldn't put a robo in a Hamster Heaven or a cage with 1cm bar spacing. The narrow bar spacing of the Mickey 2XL is way better for them. How is the door stiff? Do you mean fastening it? I developed a technique for closing mine onto the second bar (ie tighter closed fit) without it being too noisy - just kind of doing it slowly and pulling it onto the second bar. You can't close it on the first bar as it leaves a gap that a robo could get stuck in.
Despite it's low height it did seem surprisingly high with a robo in it and they can scramble up the bars sometimes, so set up needs to be done carefully, but I'm sure you already know that.