Aspire 10.5 importing an STL files

I am trying to make a plaque.

I can create a toolpath for the profile, but when I make one for a pocket the central graphic is carved away just leaving a from.

I can use a V-carve toolpath but this is intended for V or bullnose bits. I want to use a 3mm endmill and would the toolpath to take into account of the tool size.

Is this feasible? I have added a zipped stl file of the intended item.

Is there any other software that can achieve this? Preferably open sourced!