I have 8x6 on both of my bikes. Looks much better than standard without attracting any unwanted police attention.
I've used THESE for the last 4-5yrs. Not as cheap as eBay, but you can order suitable nuts/bolts n sticky pads etc. too.
I normally run with 7x5, never had an issue after stopping and talking to the Police many times. Got a 8x6 on my Speedy, but that's mainly due to the size of the mounting plate it fixes to.
Edit: Never had to change them for MOTs either, but I guess that depends on how well you get on with your tester![]()
Technically classed as "show plates", but basically the same as normal plates bar the size and dealer name etc.