Here it is what ended up happening for me!
I worked on my propane tank mounts today and got them up and running. I had purchased a set from my local welding shop that open with a hinge then tighten with a wing nut (like the ones linked in post #21 by Big Geek). Once I had them in hand they didn't fit the tanks

and they made the tank stick out nearly 2" from the sides of the trailer... not good... not only that but they were 60 bucks and not close enough to what I wanted to justify the cost, SO...
... I made my own!
I started with about 5 bucks in scrap material from my local steel yard. I cut two channels 8" in length. I drilled three holes to make my mounts foundation.
Next, I welded 2x.125" strap to the sides of the channel and hoisted the tank into place. I used the tank as a mold and started to bend the strap around the tank... I used a few ratchet strap to hold the tank in place and I screwed the foundation to the saw horse, this all worked really well.
Then, I tacked in the short side. I bent the tab over and then got the rough shape by bending the steel in my vice with a 3lb sledge. If you try this, just bend it a little at a time and after a few minutes a nice smooth curve starts to form.
Once the short side was in place I could trim the long side to the right length. Then it was time to burn in the welds, the first one I made the spot welds failed once I really started getting after the bending.