This work was a good reminder why I chose not to set all the rivets around the areas where cross members and vertical frame members attach to the rest of the frame. There is not much room for drilling the bolt holes for the ends of the cross members.
By the way, I was NOT able to find where it calls for the bolts to attach the cross members to the frame. I searched the prints and I don't believe the information was there - pissed me off a little bit. The only reason I know is because of a set of videos that I purchased of a OneX build.
I'm completely wiling to be wrong but I was not able to find it on the prints.