After completely clecoing the tailcone back together, I started rivetting the the assembly together this afternoon. Rather than first rivetting the vertical channels to the side panels first as per the plans, I decided to take out every vertical channel / cross tie assembly one by one, rivet it together and cleco it back in place. This way I have much easier access to those rivets in the corners that would be too close to the side skin if you'd want to use a pneumatic rivetter.