G'day again moweasy,
Confession time! I'm a sinner!
I just use a couple of 12" shifters or knipex parallel jawed multigrips. If you've not seen them they are a nice piece of kit that don't put teeth marks into the job while applying all the load that a normal set of multigrips will.
I know it seems a bit rough but I guess the point is that I've never found those nuts to be particularly hard to undo.
I'll pop over to the shed and get a measurement for you in the morning.
Cheers,
