Thanks Gary,

Still have the 280 mains and didn't feel much of a difference between them and the 300's to be honest. I think the bigger mains have ironed out the stutter but am thinking the pinking may be over advanced ignition (running a tri-spark set up). Have been told to back off the back plate slightly - will that be a counter clockwise rotation to retard ignition? Can't recall...been a while since I played with points, timing and the like.

The plugs pulled out reasonably clean after the weekend's run. A little sooty but no signs of running hot - electrodes fine, no 'ashy' residue.

I take your point about not loading it on the hills, keep them spinning has always been the advice I've had but was a little worried about over-revving a new motor. Will snick her down a cog on climbs now...I'd be a mess if I blew it this early in the relationship! hahaha!

Always good advice, thanks for the time!