What I have seen done on a similar-rig Ericson model was that the rigger put his head down on the deck and sighted up the walkway. On the boat I was watching the deck had a slight upward bulge -- so the interior threaded rod was cranked down a little bit until deck was level. This was over a decade ago. I have checked the deck on our boat and it's level, for whatever it's worth.
Be sure to lube the threads top and bottom for those big Navtec ss rods inside; you don't want to gall the threads.
Also take a look at the tabbing on the inside structure where those rods are dead-ended. I hope that the prior owner never allowed water to run down the rods or migrate into the deck coring, either.
Others here may have more recent or pertinent observations on the process, too.
LB