For some reason, I was really paranoid about messing this up. I must have measures, clamped, unclamped adjusted, and reclaimed a dozen times. Also had to shorted one of the longerons another 1/16" or so to get the firewall to nest appropriately on one side because the firewall weldment was hitting the longeron before it was located per print. It was such a small amount that I didn't want to hack at it with a grinder, so I knocked it down with a vixen file. Note- The print says that the AFT side of the firewall should be 5/8" aft of the leading edge of the F-770 skins. The instructions give that same measurement from the FORWARD edge of the firewall. I figure that it's going to be pretty much impossible to accurately measure this to within a .020 or whatever the firewall thickness is anyway, so I elected to get it as close as possible using the fwd dimension, because it's easier to measure. At any rate, I clamped this thing up with about a million cleco clamps and 3 sets of vice grips on each weldment. Walked away, had a cup of coffee. Came back, remeasured everything one more time. Then drilled in the sequence called out per instructions. Came out fine, and only got cut once by stainless steel shavings :)