Seconded. I faced exactly this problem with my Douglas Fir frame. One of the last girts to be cut had dried sufficiently to result in a clear twist. I snapped chalk lines to mark the tenon width and others to mark the base of the seats for the joists and the depth of those seats. Then I cut from those lines. The resulting beam was actually the easiest to fit in the frame since the tenons were perfectly aligned, unlike those cut using edge square rule where the slight twist acquired by the beams required "persuading" with a very large lever.