Splatt,
The dual coil should fit, what type are you using?
The buzzing could be caused by the rod, it may be incorrectly set and loaded up. You need to set it up with the bike off it's stand, you onboard and the rod bearings should rock freely.
Never saw the spring thing any where else, it does work very well where it's at. To try it in another position you might find it's a bugger to set up. Anyway, I reckon it's a bit of black magic and should be left where it is :roll: .
Cash