Yes, if you can do that for both the cortical and deep sources, it may works, and still you need to refine in order to reduce the instabilities.
Im not sure if this function support the FEM mesh yet.
I have implemented a version here, few moths ago not fully cleaned, but it may works,
the main change is this function:
with an extra menu item when you click on the FEM mesh, => refine mesh => refine around xxx
At least it will give you the idea how to refine the mesh.