2004 was sort of a half hearted attempt to do something but it certainly lacked follow through. 2005, they came out with the full slider with extra storage. That leaves no reason for putting horizontal tanks in the 2004......just venting.....
Both of my tanks only took 3G of propane when I had them filled. They were both "
Empty" (at least no propane would come out). I always got at least 4G-4.5G on my vertical tanks. I thought it was because of the design of the valves on these tanks.