Its time to assemble the Lithium Tower of Power!
I purchased 8x 1.2m x 6mm galvanized threaded rods from Bunnings at a cost of $3.77 each. I used some loctite on the end of the thread and screwed each of them into the mounting base. I hope its enough to hold when I tighten down the modules from the top with a nut.
I then stacked the modules. I will wait for the loctite to fully set before tightening down with nuts.