I haven't used CamBam for many years but vaguely remember there was a setting to do an offset pass (say +0.5mm) larger than the part. This is the roughing cut. Then pick the actual profile you want and run around again, taking off the last 0.5mm. This is the finishing pass.

I create an offset path in CAD (very quick in AutoCAD) and create the 2 toolpaths accordingly. I don't cut much Aluminium but remember reading that you ideally need to leave a reasonable amount on for the final cut as it can work harden with the roughing pass then the finish pass tries to cut through the hardened part which reduces tool life. You need to cut underneath it (the work hardening is not very deep). I hope someone else can expand on this or put me straight if this is misleading, but that is my understanding.