Any reason you're not asking your insurance company this question?
That's a dodgy game to play, if you don't disclose facts that are relevent to your insurance cover you may find that when you need to claim they'll state your insurance is invalid because you've withheld facts and you have no cover leaving you to pay for your own and 3rd party expenses, that could leave you in debt for life. I for one would have though that you would be advocating being straight with insurers !?!I bought a cat C bike last year. My insurers didn't ask and I didn't volunteer the info.
I adjusted the bike value accordingly as no doubt they would if I ever claimed.
I'm pretty sure the insurance company will know the category when you give them the reg.