Central Spark Plugs

Hmmmm, some interesting replies and I have enjoyed reading the comments. My original hypothisis that some improvement could be gained by centralising the plugs came by observing the difference it made to Triumph motors running in a dyno. while I suspect there would be an improvement re the Norton I also suspect that it would be far less than in the Triumph due to the different combustion chamber/piston crown architecture. I believe that a Norton motor, with it's more shallow combustion chamber and relatively flatter piston crown will work very efficiently with a carefully set up squish band. Perhaps, if I ever get the time I'll be able to try out the centralish plug theory in a practical sense but for now I'll go with a more conventional approach.