After assembling the aft fuselage, I tried to install the aft fin spar but notice interference with the external strap I installed to reinforce the lower doubler. To solve the problem I simply rebuilt the lower doubler. (recall that I built the external strap because I did not like the edge distance on the doubler, but saw no need to rebuild the doubler just for that at the time) This meant I had to drill out some of the lower spar rivets etc etc.
