I run 10mm ones on my race car and have had no dramas non hubcentric either...

As for coppers well there's two ways you can play it..... don't do anything to get pulled over.
or when asked (most coppers won't know anyways) tell them it's a dust cover like the new fords have. If it os obvious that there is a spacer ie: supercheap one size fits all.

I know of a group of people who have alloy "hub extensions" on their cars who race and have no issues with them coming loose or breaking.

to make it a hub extension and not a spacer it has one screw in it connecting this item to the hub so when wheel off occurs it doesn't move.

oh and no such thing as a red sticker anymore, just a yella one sideways in the middle of yer screen.