I started riveting the tail cone. Various builders before me seem to have used a back riveting procedure to rivet most of the tail cone, so I thought I’d give that a try. I assembled all of the bulk heads per the plan procedures, but left the top of several bulk heads cleco’d for now, just in case that helps later on. All went well with the bottom skin and stiffeners, until I started riveting the left F-1029 bell crank rib assembly into place. After setting three rivets, I had a look over the remainder and was shocked to find a missing dimple. I checked every part multiple times during and after dimpling, but clearly missed this one. Luckily I only set three rivets before noticing the problem; no choice but to drill them out so I can deal with the missing dimple.