thing is though you can get everything pressure tested and safety checked and think your safe but theres always the chance of something failing. In my feather i had a 12mm pushfit elbow blow up and go flying off like a bullet, i should have been wearing goggles but i wasn't tbh but it was all within the robot at the time so i avoided any harm to myself. but you can think everythings safe and un expected things can still happen

i've used the ali camping bottles before as buffers and i've never had one fail. in my experience its the fittings that are more of a problem area