this is the code i used to cutoff the ring ..
G00 Z10.0000
X0.0000 Y6.8000
G01 Z-5.000 F150.0
G17
G03 Y-6.8000 I0.0000 J0.0000
Y6.8000 I0.0000 J0.0000
G00 Z50.0000
G00 Y0.0000
M05
M30
now it occurs to me this should be reasonably simple to setup in mach as a macro that will popup a dialog box and ask me for Green = ((Fingersize/2)-(Cutter Radius)) and Red = (Depth below Z0) then run that code?