Just watch out for inexperienced fillers. I had one stop at just over 5 gallons because "they shouldn't hold that much", He thought they were 20#.
I also had one PFJ where the kid said he could legally only fill two cylinders, not all three I had. He said his manager told him that was the law. I got his managers name, and then I called PFJ corporate. Turned out that wasn't his managers name, and, of course, they corrected the store (while I was on the phone, no less). Never saw that kid there again.
I had similar, filled 6 20 lb cylinders for deer hunting trip. I was transporting them in the back of a half-ton van. When the pressure relief valve popped on the first cylinder, I couldn't see my hands on the wheel. I took a half breath, leaned my head to the open driver's window, and slowed to a stop on the shoulder, turning the key off when slowed. Turning that key was a long moment. One spark and there would have been no van and no me.
Later, two other cylinders released. The cause was certainly over filling.
Unfortunately, this fill station had a tragic accident when a kid filled a cylinder that a previous user had filled with acetylene. That should never have been possible but the user may have done that himself. The fill station exploded, killing the kid filling and damaged the nearby building so that it was closed for repairs for months. Be careful out there, propane has a lot of energy.
