A good way to handle the measurement process is to use a nail in a board so you can
anchor the  wire while stretching it out on the floor or driveway.

Be very careful with the measurements. It is not fun to have to solder a piece back in that
was mistakenly cut off. So remember the
old carpenter's adage;

Measure once; cut twice or measure twice and cut once.
Step 4 photo 2
Hex beam by K4KIO