I started with the table to get a good base for the Lowrider V2.
The depth of the built torsion box is 8.25 inches.
Four full size 3/4" sheets of MDF later, I have a sturdy (and heavy base).
(The leg leveling kit off Amazon is awesome)
I’m using full sheets of MDF top and bottom and using them as a reference for the torsion box and side rails.
The side rails are (2) 3/4" BB ply strips with channel strut bolted on.
The side rails are slotted at the ends (to allow vertical alignment) and through bolt to brass threaded inserts into the torsion box (each side of the torsion box is double thick).
I know I need to brace the legs (and will), but this is rock solid as is.
Pics attached and will post when I get the rest assembled.