[velma]

I've used a 6.5" silent spinner with my old robo and also the wheel that came with his tank which I think is 5" and they both suited Hector fine. The spinners (I currently use a p@h one) are thicker round the edges so may be harder for a wee robo to get his teeth into. Cypher is right - saucers can be a bit tricky to keep in place. I had one for Hector in his play tub so wasn't on much bedding and they do bounce a bit. And there is something very tempting about that base which they seem to want to get under. It may work out better if you can try him with a smaller upright wheel. It does seem to take them a couple of days to get used to them but they're usually finewhen they do. In the meantime, not sure if you can build up the bedding under the saucer & make a nest entrance under for him to try and encourage him to go in without chewing? Or maybe, instead of a shiny tile try it on a wooden house? Some of them are quite big and flat topped so could act like a little level. If it's the ones finished in rough bark it may give it some grip?

Everyone has different experiences of what works for them & the set up they have , wheel included. So there isn't one right answer. And as all hams are individual it makes it even trickier. What works for one may not suit another but I'm sure you'll find a solution that works for you.