Cool! Was looking around myself last night and yeah I think I see where you're heading MMD.
Also regarding the fill level, everything I'm reading says that this system will deliver full power right up till around 15 seconds before it's empty. So, and this goes hand in hand with what you guys are saying, a gauge is pretty much useless.
On that same note, I've read several warnings (suggestions); don't trust the guys who fill your bottle. Instead, take your new empty tank and weigh it, valve and all. Save the number (some tanks already have it imprinted on the side). Then when you get home weigh it again and make sure the new weight has increased exactly by the rating of the tank; for example if you have a 10# tank, lets say you weigh it new to be 14.5lbs. When you get home, make sure its new weight is 24.5lbs. If its more, bleed out the extra until it is.
Apparently a properly filled tank can be half buried in the Mojave for the summer with no problems. On the other hand, even a slightly overfilled tank when exposed to ambient temps of 100deg or more, can and do blow (the one-time-use safety valve blows and you lose all the CO2). I guess there's some exponential relationship between # overfilled and pressure build in the tank. It only takes one or two #s over to cause problems.