Did you balance the complete wheels again?
I was referring to a very low quality, direct tailpiece, type of safe, (an old Sentry) not a key change style with quality parts. This was on a personal safe when I had way more time than productive jobs at that monent. Doing this is definitely not commercially cost efficient for a paying customer.
Just brainstorming:
Regarding your idea to wrap the fence and then file it to sharp edges, won't that thin the wrapping metal to the point that it will break at any corner? Unless you plan to braze/weld the new piece on, then you will have solid metal to shape as you wish.
A 'U' shaped piece of brass could be folded over the fence with the ends facing the wheels. Then solder it in place and file to the exact size. This does not change the distance to the wheel.
Another idea might be to knock out the original fence, drill and tap the hole, screw in a brass screw that is larger than the original fence, peen over the screw threads on the back, and file the new fence to the exact size desired. You could use a trapezoid shaped bar and solder it in place, as many fences are, but filing out this shape hole will be a lot more trouble.
Squelch's idea of using square tubing is a very good idea as the corners will be sharp enough to rely on. If it slips over the fence tightly you could then apply a little solder with a torch and the result will be just about permanent.