That is really not an option. The fitting at the top is contoured and not a simple tube shape, and you would be trying to jury-rig a dump cable as the one you have now is two segments each with a terminus at that mid hose QD. That QD is also how you pull the dump valve without removing the regulator from your mouth.The aqualung hose has a disconnect so you can remove the safe second from the tube so I'm not sure I'd be able to swap it out but I'd consider that.
You never answered whether you are just testing, or using this as a primary.
And if it is sealed in your mouth but still breathing wet, it sounds like there might be some other issue.
And maybe a longer LP hose is needed?