Yeah I think the BOM is short 2. I experienced the same. Maybe @spraynard can update for the 6 instead of 4.
Dammit I thought I updated that.
A “fix” is to only use two 45 degree supports on the bottom, one left/front, one right/back
I find these perfect.
Easily adjustable and they hold the position firm
These particular clamps work great for the square 80/20
CAMVATE Camera Clamp Mount for… https://www.amazon.com/dp/B018RMBCR2?ref=ppx_pop_mob_ap_share
They are out of stock on amazon, but they have similar styles ones
Edit: not sure if that link works. Here is a similar one https://amzn.to/2Mms9hc