Tom,
I did my longerons and bent and bent and tweaked until I couldnt stand it anymore. I laid them on the floor and decided that was as good as they were going to get. I put them back in the garage attic, where they stayed until about two weeks ago.
I have my longerons installed and the firewall mounted (today) and, man, those puppies are as close to perfect as they could possibly be. Just keep tweaking until you have that magic 1/16th of an inch I used my digital inclinometer to get the 17-deg twist. I was sure I would have to further twist/bend/beat/squeeze or otherwise abuse my longerons, but that was not the case.
PS: Measure many times...beat once.