My bottles stand up and they have a crossbar and huge wing nut that pushes the crossbar down on the tank necks to keep them in place. Gravity sucks... The crossbar always gets in the way when changing tanks. I put a collar on the center rod and drilled A cross hole for a drive pin and put a spring on top of the collar that pushes the crossbar up when I loosen the wing nut so the crossbar always goes up and stays out of the way. Craig