I know them and I don't like them for attaching a cylinder. They are rather bulky.Do you have access to an Over Center Buckle?
Stainless Steel OVERCENTER BUCKLE 304, STANDARD 1 in.
Stainless Steel OVERCENTER BUCKLE 304, STANDARD 1 in.stainlesssteelmarine.com
Truck stops in the US have them for sale for about $10.
They are used for cargo tie down.