It's important to isolate the fuel tank from the chassis to reduce stress and vibration that can lead to cracks or other failures. It's also critical that it stays put in the event of an impact or a roll over. It stores and 19.2 gallons which equates to about 116 pounds which, when multiplied by whatever Δv (hopefully small), means that you want to ensure that it's well mounted.
The tank is positioned as far as possible to the passenger side to provide better weight distribution when there is no passenger (I'm also a little heavier than my wife!)
I was going to fabricate brackets from 90° angle aluminum, but I found some nice ones from 80/20 Inc. They are clear annodized and gusseted for extra strength.
The self-adhesive rubber was cut to size and applied to the chassis and brackets. Two small brackets were installed to support the lower rear of the tank. Since they partially sit on welds, the bottoms needed to be machined for them to sit flat. Two large brackets were mounted on top of the tank and one large bracket was installed on the side of the tank to keep the tank from sliding to the driver's side (the passenger's side of the tank is stopped by the chassis).
I think that I'm going to install one more large bracket on the large cross member to prevent the top of the tank from tilting backwards, but I'll need to pull the engine to gain access.