Arkie, I woke up dreaming this morning about eliminating one of the unwieldy stop wrenches from my design. I will post the upgrade here today, barring any unforseen eventualities.
In order to give you maximum satisfaction, I want to know what size machine screw you have in mind, plus the gauge and dimensions of your square tubing.
Smaller gauge RivNuts install like pop rivets .
You COULD get a complete kit from Horrible Fate, but you might end up with Daswulf's frowniface.
Shown in this thread are 1/2-13 overkill nutserts, but they come in virtually any size, imperial and metric. Below is the link to my Candy Store:
http://www.ababaqa.com/
Robert Taylor