UV Map Scale

I’ve created a model with polygon hair. There is a lot of it and it is in (5) objects to give me control over different areas and make it easier to work with.
I am ready to create and apply UV maps to the different hair strands.
I know how to create the UV maps and export them to GIMP to paint the hair.
The Problem:
How do I get the scale consistent between all (5) maps so that the hairs look the same diameter? The hair strands in some objects are short while the strands in others are long.

Here are a couple images of the hair. The hair objects are different colors.