Damn, it must be nice to have that kind of budget and time to come up with all this. How about just filling the can with water until it reaches the bottom of the OVERFILL TUBE that should be in place. If its not, its surely easier to just replace it (so it can be refilled anywhere there is water and compressed air) than concoct this rig. You might also check the current regs on refills. Many states do not allow anyone not "certified" [i.e. licensed by the State] to recharge any extinguisher. This is partly due to a Brother refilling a can directly off an SCBA cylinder and blowing it up.
