Both the folks at VAF and at Vans said to twist the longeron more to improve their fit to the engine mount brackets. Measuring the twist of the longerons, they seem to have "relaxed" about 4 degrees from the original twist. After that I removed the firewall and un-clecoed the side skins forward of the F-704 bulkhead. Photo 1 shows the setup for increasing the twist. Since the engine mount brackets seem to be straight, I removed the couple of degrees of twist along the brackets, then increased the twist from that point aft. After several tries I got both sides to 17 degrees .
I then re-clecoed the side skins, re-clamped the firewall in place, and clecoed the bottom forward skin in place. The extra twist I put in the longerons is still not quite enough as evidenced by the fit of the reinstalled firewall (photo2).
I think for the next work session, I'll remove the firewall again and measure the actual angle of the brackets then twist the longerons a degree or two past that. Even if they don’t relax, it seems to be much easier to reduce twist than increase it.
brackets. This is the setup to add to the twist without removing the longerons from the fuselage.
Better, but I think it will take one more iteration.