Hello rlrhett,
I am sorry for the delay. I have been very busy finishing madCAM 4.0 for release. It is available for download from my web
www.madcamcnc.com.
I think you already have figured out how to do it but I hope this will give you some help.
madCAM is designed for cutting out 3D models and not cut in surfaces on the model. The stock to leave is a 3D offset used for leaving material after Roughing or if setting to minus amount, used when cutting EDM graphite electrodes. The negative amount of stock to leave should never be more than half of cutter diameter. The only way to force madCAM cutting into material on the model is when using 2,5D functions or with the Along Curve command. The Along Curve feature will create toolpaths that follow curves exactly as you draw them in Rhino and the rapid traverses will be calculated from the 3D model.
It is also possible to use Project Curves and Along Curves in combination. You can use the project curve for getting a toolpath curve in Rhino. This curve can be modified as any curve in Rhino and you can modify it and use Along Curve for making a new toolpath of it.
If I would cut a slot on a curved surface, I would make the model in Rhino with the slot included and then cut it.
Joakim