I am starting the build of my Roubo workbench. I got some DF 12x2 sixteen footers that have been stickered and acclimated in my shop for the last 5 months or so. I ripped a couple of boards to 4.5 inches wide and cross cut them to 7 feet length to start the lamination process for the top. Unfortunately, I am facing much more twist than I hoped for. Yesterday night, I tried my hand at one of the boards and started with winding sticks on the two far ends of the board. With my scrub set to a very heavy cut, I removed the high spots on the first 12" of the two opposite corners at each end of the board and then moved one winding stick closer to correct the twist on the next 12". I left the other winding stick where it was and did not touch the area anymore with the planes, since I imagined I needed to keep one side as a reference for everything else, otherwise I would mess up the previously 'de-twisted' sections. In this fashion, I went on removing the twist along the entire board. I then identified the high spots with a straightedge and removed them with cross cut passes with my number five. Finally I started with full length passes with the five and finished with my No 8.
Making it (reasonably) flat on one face after removing the twist was easy, but getting rid of the twist was a lot of work and required constant checking (unfortunately, a few times I went too far, which forced me to compensate on the other side, with the corresponding loss of width). I have read about how to remove twist on boards, but never found anything specifically addressing long boards such as these. Are there any special considerations/tips for long (and not too wide) boards? For instance, was my decision of 'anchoring' one of the winding sticks on the far edge and not remove any more wood on that side after the first step a good one, or should I have done it differently (like trying to remove the twist at once by moving consistently along the entire diagonal?)
P.S. How would you decide if the twist is just too much to even bother? I am using 36" winding sticks and they do a great job magnifying the twist... so great that makes me wonder if I am just dealing with a board that is simply unworthy: To my untrained eye, I estimate twist of a couple of inches at the end of the 36" winding stick (which is balancing on center). This is my first attempt at flattening anything by hand, so I have nothing to compare it to.