In the vertex modeller, try mapping each group parametrically (a.k.a. flat mapping), unless the group is topologically similar to a primitive (cube, sphere, cylinder). If you're using UVMapper Mac 0.2.9, you can make one of those "multi-layer" templates that includes all the parts, and you can delete groups from the "multi-layer" template to save individual templates for each group. ISTR there's no "Delete" command in UVM 0.2.9 (one of the many reasons why a UVM Pro version is needed), but you can shrink and drag parts off the screen to simulate deletion.