Linear bearing made of three bearings

UPDATE:
-
Cleaned up some support lines

Added a weight saving option to cut out some unneeded bits.
Fixed some errors where supports didn't reach all the way.
Added comments to the code.
Description
--
I was looking for a new linear bearing to use for the x carriage on a printer. This is my first attempt, and f me it works. It's not very parameterised, I'll look at changing that later.
Currently it works with 623 bearings (10mm wide, 4mm wide, 3mm hole in the middle).
The n