I tried it, but Mach 3 now complains about the radius of the arc being smaller than the cutter after compensation. I think the problem is the lead in path.
Meanwhile I have generated a different toolpath with the offset function in BobCad. This function essentially creates the compensated toolpath.
Of course that means deciding upon a tool while doing the CAM, but it worked like a charm.
Thanks for your help!
Bart