I cut the forward edge of the F-717-L Lower Longeron so that it would fit properly against the firewall. I accidentally nicked the part with my Dremel. This damaged area is more than 2X hole diameter away from the nearest hole so I’m not concerned about this risk.
The F-713 Auxiliary Longeron didn’t quite fit right against the firewall and the F-717 Lower Longeron. I marked the interfering area and cut away the excess material. 
The image below shows the improved fit of the 3 parts.
