Until you get a better answer....
I have a 1999 Curvy so my C-spanner spec may not help but I have just tested the old way I used to do my old Hondas rear shockers adjust on my,"Curvy" using a pair of these,
http://www.diy.com/departments/value.../605663_BQ.prd
http://www.ebay.co.uk/itm/Neilsen-25...1%26rkt%3D1%26
Worked pretty easy even on the side-stand.Would be even easier if the rear wheel was off the ground<Paddock-Stand).
Useful tool to have around anyway if you don't have a set.
HTH