Congratulations Wingman!
I believe you found the best solution.
Many (but not all) full plate 18 size American watches will assemble much easier if assembled upside down rather than from the pillar plate. Some models like the Waltham 1883 can be built from the piller plate as the top plate can be tilted and the pallet inserted into the potence from between the plates. Most other models, like yours go together easier the way that you did it. This topic has been touched on a couple of times before in this forum... If you would like to take a look then see
viewtopic.php?f=2&t=58&hilit=upside+downEnjoy!
Bob