Funny that this thread should pop up!
I've just stripped and greased the swinging arm and suspension linkage. I also have excessive slop at the frame end of the suspension linkage.
The bolt is 11.5mm and the bush (slightly oval) at 13.3 - I haven't measured the slop at the bush ends (I didn't think to).
The other bush's bolts are a nice fit - the play on this is very visible on the bench. Worse on the bike, as can be seen in this Youtube video:
I can readily get shims from Namrick (the Nut and Bolt shop round the corner from me) but it's a major pain as I had to put the bike back together to get it back in the workshop (there's more room outside!).
Oh well, hopefully the shims will fix it. I need it back on the road as I'm off camping near Chemnitz on the 7th Jan.