Thanks Ger,
I was hoping to keep the CAD side of it as simple as possible. I drew the centerline paths in Rhino and used Rhinoscript to generate the g-code. I failed to use the G40 word before changing the compensation so I'll have to try inserting that tomorrow to see what the effect is. It was suggested to me on the cnczone g-code forum that I would have to use leadins with the cutter compensation change so if that is in fact a necessity it may make changing the CAD the easier solution.
Chris