Per the plans I cleco'd then riveted the aft deck on (see photos). The instructions said to not rivet the elevator stops where they go through the aft deck for removal and adjustment with the tail fitment much later in the build.
The flat plate setting on top of the upper longerons is the aft deck -here it is cleco'd into position
All the rivets drove well-didnt have to drill any out. I did squeeze the ones that had access