I know this should be easier but...
You should change some values in the theme you are using.
Change the following parameters in the appropriate Metacity XML file.
Clearlooks-Phenix's theme is located in /usr/share/themes/Clearlooks-Phenix/metacity-1/metacity-theme-1.xml for instance.
The following parameters control the width of the borders and consequently the width of the re-size area:
"<distance name="left_width" value="1"/>"
"<distance name="right_width" value="1"/>"
"<distance name="bottom_height" value="1"/>"
By default they are set to "1", but I found that changing them to "4" doesn't change the appearance very drastically, but makes it very much easier to re-size using the mouse.
I changed mine to "6". Human (my selected border) located in /usr/share/themes/Human/metacity-1/metacity-theme-1.xml
See also - https://ubuntuforums.org/showthread.php?t=439329
Good luck @Brian_McGonagill .
Edit: I messed up on the formatting, now fixed.