Now we can mount the bottom plate of the upper deck to our arm/boom sub-assembly. Of the two deck plates the bottom plate is identified by four extra holes (below two photos).
These four extra holes are for fastening the plate to the arm/boom sub-assembly that we just built. Once you have identified the bottom plate mark off the four extra holes with a Sharpie marker because we don't want to fasten any stand-offs in these holes. In the photo below we have marked the sub-assembly mounting holes with a silver circle and the stand-off holes with a gold "X".
When fastening the stand-offs in place, it is a very good idea to use some blue Loctite Thread Locker on the threads of the screws because once the deck is fastened to the arm/boom assembly these screws will not be accessible if they happen to vibrate loose (below photo).
Once the stand-offs are all fastened into place, this upper deck sub-assembly can be fastened to the arm/boom sub-assembly with the nylon locking nuts (below photo).
When we position the power distribution system we will find that it is very close to two of the nuts, so to protect our hexacopter from any short circuits in the event of a crash, we are going to insulate these two nuts by placing some heat shrink tubing over two of the nuts (below photo).