I have too 'modify' my HB with a hammer today. I am fitting some 185/65 13"s on 6" Vega ? wheels from an HS I have borrowed.
As far as I can see its the little bulge just to the outside of the square recess that need tapping in. I need to take more away on my front guards at the bottom corners (I think HCs are OK here?)
You could send Coggers a PM as he has much wider wheels on his Viva I think? See here...
viewtopic.php?f=22&t=8409alex