Setting the control tubes in the cockpit in place. There are 2 elevator tubes. The rear tube is missing parts to rivet in place. Also, a Service Bulletin came out today (6/30/20) for a control tube stop to replace rivets. Much time spent figuring out exactly where the factory is referencing. (7/1/20) Figures out the service bulletin with a military aircraft mechanic buddy and we complied with SB#12.