I bolted a 2x4 frame on the inside of the truck bed wall and use these offroad straps to secure tanks vertically. Hundreds of trips with multiple tanks and they are rock solid. I use them on my boat too.
Familiar with the Quick Clamp products (great kit) from my overlanding days.
As advertised, ”Holds 50 lbs”. A twinset is already well past that in a static state. Add some momentum from a collision and I think the odds of material failure (hence a loose tank and a bigger problem) start to go up significantly.
I think what works on a boat is not necessarily applicable for highway travel where collision with a hard object is a much more likely contingency.