Yeah, although a rear shock would be the best solution, it's just way out of my price range at the moment.
I have been looking at the hyperpro springs, I've read on a few forums that using the DL1000 springs on the 650 is a good option too, but I don't know if they'd be the same dimensions?
Will be looking into Faulkners springs too, I think your dimensions are pretty dead on from what I've seen.