I tried once and the wheel fell off the stand. Didn’t trust doing it after that. It is not held into the stand by anything. Having said that I’m assuming you mean the plastic trixie wheel. The wood trixie wheel I do have upside down. Take the base off and use two large washers on the outside of the cage then put back the screws that held the base on. So the screws go through the large washers, then through the top bars, then into the holes in the wheel stand where they were before- with the wheel stand inside the cage obviously. The tricky bit is holding the wheel in place while you screw through the stand. I managed it on my own but easier with one person holding the wheel and one doing the screws. It’s very stable and spins better
. Because the wood ones eventually sag and start rubbing against the base of the stand. That doesn’t happen when they’re upside down.