Nice job....thanks for the video!
Similar to how I built mine except I went with double width BB, and didn't use any cross members or vibration / isolation devices. Just (4) 80-20 uprights and BB shelves bolted solidly onto L brackets. Top shelf is wider than rest and bolted down into 80-20 threaded center channel - no L brackets. For levelling and sliding across the floor, I screwed hex bolts into bottom of 80-20 posts and glued some sliders onto bolt heads.
I have since modified it into 3 shelves by cutting down the uprights and removing one of the shelves.