I do the same. My inflator is designed with a hole in the bottom of the container part, so you can insert a cartridge upside down and still screw the top on fully. The nipple on the cartridge sticks out the hole in the bottom. When I need to use it, I unscrew it, turn the cartridge around and rescrew it. That lets me carry one more cartridge than I would have been able to otherwise for the same amount of space taken in my bag.