There's always the RAM mount yoke clamp option that I've used for the past 3 years - clamps to the ignition barrel and now I have no use for it can be had for the grand sum of £5 including the rubber shim.
vienna, Do you want to add it to the plugs?
If not, any other takers?
Adam
Forgive me father for I have sinned... ex S owner moved onto pastures new with four cylinders and a chain... and back to a twin, albeit in a V.