Make sure the safety isn't on.
On Pumas and Bobcats the safety would wear and cause the gun to fire multiple shots when in safe position.
Back in the day you use to be able to send them into ICD for the "tournament" trigger mod where the milled the trigger so it would fire only once when the safety was on but the pull was shorter.
I am pretty sure an alley cat hammer will not fit in the Puma. there is a considerable difference in where the sear catches on the bolt. if you put one in and tried to cock it it wouldn't catch on the sear.
position of the siphon tank on the gun will not make a difference if running dual bottles, but if you run just the front tank under the barrel you will have issues. its why ICD switched front hangers from able to fit a 12oz to only excepting a 9oz. if you only use the front hanger it needs to be vertical.
The other issue could be the front hanger is not opening the valve enough to get good flow.