I assume purpose is to ensure there is no air in the cylinder - disconnecting the output will drain fluid after that, but as long as the opening port remains submerged, there should be no impact to the cylinder - is that correct?
I left the plugs in place 'till I had all my hard lines bent and ready to install,only at the last minute did I remove the plugs and quickly fit the brake pipes.
Fluid loss was minimal and I simply bled the system as normal.
I did it the old fashioned way, i.e. no fancy vacuum bleeder!
