The uncertainty of this gun being cocked and staying cocked is a problem. In releasing valve guns such as the GSD models the different pressure existing on either side of the valve plug in the cocked gun keeps it firmly closed as high internal air pressure is trying to push the valve plug down the inner barrel, the opposite direction to that in which it can move in order to open up and thus shoot the spear. In a "Zelinka" the releasing valve is mechanically held shut by the trigger mechanism's catch element that blocks the mobile inner barrel (which is actually the valve body) from moving as air transfers across into the outer pressure reservoir during muzzle loading via a completely separate, expanding rubber ring type valve that does not involve the releasing valve opening at all. So provided that these valves don't leak the gun will stay cocked. If they do leak then the air flow is so restricted that the spear only moves slowly out of the gun. But on a balanced valve gun, such as the one shown in the preceding diagrams, you will not be so sure as any air leak via the rear sealing ring (which traverses the inner barrel windows or side ports during operation and therefore risks damage!) will blow the releasing valve right open, it will not just let a trickle of air through and send the spear slowly back against your loading effort when the gun failed to cock properly. Instead it will shoot with its full force, so you would want to get your loading hand out of the way of the muzzle very quickly. Of course you always do if you don't want to be shot through the hand with any muzzle loading and simultaneous cocking speargun, but here it will be likely to happen with zero warning. Basically this is because any air leak in the valve powers the releasing valve body to fully open up and completely expose the inner barrel side ports, it will not just gradually lose air through a constant small gap. For that reason commercial production of this type of design would be a risk that most speargun manufacturers would choose to avoid.