johnny, you are absolutely correct - I use UU3D and it doesn’t even attempt to fit everything to the grid. It leaves you to shuffle islands around and lay them out to your satisfaction, then you place them on the grid and hit a command to make islands proportionate and everything is scales into the proportions of the mesh. You can then rescale any island that you want to make the texture more detailed by having a bigger proportion of the UV space.
I know that UV mapper was the go-to mapper a few years ago - have there been any developments in the last few years - updated to use LSCM, for instance?
A mapper that had really good potential is Roadkill, but it had some pretty serious flaws and doesn’t seem to have been further developed since 2009?