TCC, I used the Yamaha holes when I made my pannier frames up a while back.



They are a bit of a pain to get to with the stock silencer in place, but it's only 3 bolts to remove it and it makes life easier.
You'll have to-
remove seat
undo grab rail bolts from under plastic buttons (small flat screwdriver and 12mm socket)
remove plastic cover from rear rack (10mm socket under the back on 2 x nylocs, 4mm allen key on the four button head bolts)
This allows the rear light assembly to be moved forwards.
loosen the exhaust link pipe clamp (10mm socket)
Undo and remove the two bolts holding the silencer in place (12mm socket) and slide the silencer towards the back of the bike (I stand with the back of the bike in my gut and a hand either side) and then remove the silencer.
You could make a very simple bar that ran straight from the top hole to the pillion pegs (actually that's a cracking idea, bagsy).
Good luck.