Picked up some 3/16" aluminum yesterday...so I can carry on.
Transferred model to stock: LINK
Then I cut out the brackets using two different methods.
One, I drilled for relief-cuts and the other I just cut freehand with an abrasive disc. LINK
Cutting it directly was MUCH quicker, although the aluminum fouled the disc badly...but cut-off discs are cheaper than sweat.
Then, I marry the two pieces by bolting them together in strategically-placed holes. This way, I will produce exact copies.
These holes will be used when the rack is assembled. LINK
Shaping takes time....a LOT of time. LINK
But eventually (a few hours later), I end up with two matching brackets. LINK
...and now I am ready to drill mounting holes. LINK
...to be continued.