Hi Mike, when I built my stumpeater, the 3mm steel (80 litre) hydraulic
oil tank I made had a similar bracket to yours mounted on the side, and that cracked along the top weld and had to be reinforced with a big plate. It does cop quite a lot of low frequency vibration, but also would have been damped by the
oil. I notice the Brown Davis tank has the brackets going from top to bottom which would stop any flex in the walls. My two bobs worth. Not being picky just trying to help, it would be a pain to repair the tank after it has had fuel in it.