After our last conversation about Z-Axis length, I reduced it by 4″. So the machine is now 8″ shorter in the flex direction (4″ Z-Axis + 4″ legs”).
The Z-Axis is 12cm (about 5″) off the print surface (it is about 1/2″ off the table).
The copper cooler I use as square (to fit under the XYZ assembly) is 9cm x 8.3cm. So the Z-Axis is about 1mm over 8.3cm out of square.