Roborovski running too fast

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My absolutely tiny roborovki named Sonic (named appropriately) constantly runs too fast and ends up either flying out his wheel or getting stuck to the bar in the center or the side and hurtling around it repeatedly. I think his tiny body is just too lightweight for the speed he runs at. To combat this I’ve tried getting a larger wheel to potentially slow him down aswell as it being a closed one to stop him flying out the side and injuring himself as much.

Im really concerned for him as if he injures himself he is an incredibly stressed hamster who is the opposite of handtamed despite our efforts (I think he may have been mishandled in the pet shop or picked on by siblings as he was very small) hes been frantic, fast and incredibly timid since we got him and trying to tame him the normal ways leads to him getting incredibly stressed sometimes so much as to pee himself out of fear. Im not sure what I can do to stop him injuring himself aswell as to make him feel comfortable enough around me to not be so stressed.

I genuinely don’t think I could manage to take him to the vet without highly risking him jumping off the table, escaping, or getting overstressed. Just want him to be happy and healthy, any suggestions?