Is there a way to average the UV's in the UV editor based on the physical scale for the meshes? In blender you can can select "average island scale" and it will fit the uv islands/shells based on the physical sizes of the mesh. Ive attached an image of what this looks like in blender. (I know the UV's are bad, its an example). It allows you to make sure you have the correct UV size based on the mesh.
Before averaging scale:
After:
