Ok, this might be a crazy idea, but it's something I could actually use: I use clean-up passes after some 3D cuts to get rid of the small "dents" around sharp lines, and in some cases it could be an advantage to run these passes before the 3D fine cut. This means that I would have to do it after the rough cut, and the cut depth can make the smaller tools chatter a bit. So my idea was to apply the tool path to the surface, set the start depth to 0, the cut depth to a negative value, then create 2-3 toolpaths that will cut to the final depth a bit at a time. However, it seems like Aspire doesn't like negative cut depths, it simply changes it to a positive value when I calculate the tool path.
I could make some raised "helper surfaces" and apply the toolpaths to these, but it would be easier to run them at a negative depth. Is there a way to do that? It could actually come in handy for some other cuts, like roughing and fine cut, so maybe this is something that could be incorporated in future versions (kinda like the "allowance" you have in some tool paths)?