There's another old saying- - - -"measure twice; cut once!" I've had pretty good luck making mock-ups of brackets I intend to build from wood before I start whittling on steel. Wood is a lot easier to work with, and less expensive if you have to scrap a design and start over.
One of the "part time" jobs I've had since retiring as a technical trades instructor in 2011 has been inspecting vehicles for potential international buyers, to assure the quality of the vehicle they're purchasing. One client who owns a muscle car dealership in Australia has kept me busy for years, making sure he's getting what the seller claims he's buying. So far, the most expensive ones I've inspected were a very well-restored 68 Dodge Charger for the buyer in Australia, and a numbers-correct 59 Corvette restoration for a buyer in France. Each of them sold for $90K, plus shipping!
Jerry