I've done uv-mapping and tried to pack islands manually, but failed to fill the whole texture space.
But if I try packing this with blender auto-packing, it breakes stacks and I receive trashed uv-map, that I don't want.
So I wonder if it is possible do make blender distribute islands evenly, keeping stacks? Or I just need to try more and more manually? Seems like overkill though..
EDIT: It appears that 3d-coat is able to pack such stacked uvs without splitting the stacks. It actually has two variants of pack procedure: with and without 'shuffle' of the islands: without shuffle it will only move and scale the visible islands.
May be other apps can do it too, but blender can't (at least I don't see how).