Wow, it must suck to have to put a full size plate on a nice clean build. For it to look good, it can't be an afterthought. Here in Massachusetts we have tiny little stickers.
I make cool little brackets that bolt up behind the shock bolt. The bracket is slotted (as opposed to a hole) so all I have to do is loosen up the shock bolt and it pops right off so I can mount it on any unregistered bike (for tuning purposes only (of course)).