Thanks all, still don't have any decent pictures of a C subframe though!
I guess we'll have to work it out ourselves, I was particularly interested in Ivan Rider's shot of the black C, as this is the same model we have in, and the pic shows that the pannier has been retained which is also what we would like to achieve.
Honda C90 custom project thing
Suzuki SV650 waiting for a sidecar
XJR1300 with Motopodd sidecar