Something to consider: Prior to the Alvord trip I was trying to figure out how to mount a std bbq propane tank on the Blanc-Oh's swing-away without much success. I realized that the diameter was the fitment problem. Looking around I found 2.5 gallon tanks that were either the same height and roughly half the diameter of the bbq tank; or there was one of the same diameter that was half as tall as the std bbq tank. For me the tall, skinny tank worked best.
I was a little concerned about capacity because we were going to be cooking two meals a day for 6 guys for the week that we were on the run. Typically we used less than 1/2 of the previous bbq tank, but I didn't have either of those vehicles that I transported it with available for this trip. Half of a bbq tank was going to put us right on the edge.
I forgot to factor in that we no longer use propane lanterns. I came home with the little tank still about 1/2 full. If the OP's use isn't huge then these smaller tanks might be an option. They use the same valve connection that the bbq tanks use, so they're fully interchangeable that way.