Bungee down to the knobs.
Allegedly, it's even better if your bungee goes around the back of the tank valve outlet and loop around the valve extension post. Allegedly, that also allows you to use the 5th port to keep the tank more snug. I only loop around the knob because my HOG valves do not have the extension post. Plus, I kind of prefer valves sticking out to the side, rather than upwards behind. Easier to grab for shutdowns and feather with one hand without taking off bungee.
Re the picture above... Is that hose coming straight up off your 1st stage your 2nd stage short hose?
Yes, that's my regulator hose, if memory serves me well it's 36 inches (I can go down and measure if you want).
In my case, it felt like my reg was tugging down a bit, but I had the hose pointing down and making a 'U' turn up to my neck with a 90* swivel.
That's what I do, looping around the neck. I also felt it was a bit tugging, so I just put a 90-degree swivel on it, now with the swivel I feel the hose as it is seems a little too long.