Continued what's left yesterday. I took the firewall out, and twisted the longerons more to make them fit. Also, I had to do more trimming on the forward end of the longeron so the firewall can slide more in. After much debating, I decided to keep the two drilled end holes as it, this will make the firewall about 1/32" more into the fuselage, the distance between the firewall will be 21/32" instead of 5/8" called out by the instruction. I made sure this will not cause edge margin problem on the firewall flange.
The longeron is twisted more and now fits the firewall bracket well