Finally hit zero seams on a 22 yard stretch with pattern match

I do mostly residential but this job was a 1,200 square foot commercial space in Franklin, all one open room. The carpet was a patterned loop pile with a 24 inch repeat, and it was coming in 12 foot rolls. I power stretched every drop with a crab stretcher instead of my knee kicker, and I dry laid the whole thing first to plan my seam placement so no seam fell within 6 feet of a doorway. Took me 11 hours solo over two days but when I stood back after the last seam was sealed and rolled, I could not see a single line. The client walked the room that evening and said, and I quote, "I can't even tell where the pieces meet." That never happens, usually I can pick out every seam from 20 feet. I used a row finder and a straight edge on every cut instead of freehanding it, which cost me an extra hour but saved me from a callback. Anybody got a tip for keeping the pattern from drifting when you have to stretch across the repeat? I got lucky on this one but I want a system for the next one.