Using baked lightmaps as textures or: How do I get lightmap and texture uv perfectly aligned?

Hello!

What do I have to do to have the lightmaps from baked GI align perfectly with the textures?

Background: I would like to use the result from baked (or even realtime) GI in unity as a basis for hand-drawing textures in photoshop (including hand-drawn lighting). I have carefully set up the UVs of my custom meshes so that hand-drawing is easy and yields nice results, however I can't get unity to bake a useful lightmap using those exact UVs. I did set the mesh.uv2 to the same array as mesh.uv (which, in this case, covered the whole square from uv=(0,0) to uv=(1,1)), but my mesh ends up black with bright stripes and the lightmap only consists of a narrow strip of mostly black with a few bright pixels along the v-axis.

The only way I get proper lightmaps is by having unity generate its own lightmap UVs for every mesh. The resulting lightmaps however are not well-suited for hand-drawing, hence my question.