Hahaha Gauge, it's worth considering the dremel on perspex. The bonus being that if I mess one up I can just try another, without affecting the rest of the guitar.
As for the approach Frank, yeah it was freehand to a line. I was considering finishing near the edges with something other than the router, but I dont know what happened to the rest of that thought.
Will definitely be using that approach on the fix up work on the recess.