Not sure if your using Calor cylinders but if so I hope the link below may be of use to you, but would echo earlier advise do not use the cylinder laid on its side, good look anyway.
------------- Never argue with an idiot, they will bring you down to their level then beat you on experience.
Land Rover Freelander 2 & 2014 Lunar Quasar 554
I'm more surprised you can't stand a 7kg bottle upright in your front locker, not seen one that wasn't tall enough.
Anyway, I'd always recommend propane over butane.