Started with an 81 that tried to tuck things into the left 3 gaps, but hadn't figured out the trick.  Got that to an 80 and started secondary optimizing.  Then on the final night, I noticed the trick, built a 77, and went to sleep wondering how I would reduce the number of bonders.  The answer was packing things denser than the actual polymer, to allow the final segment to be built further to the right.  I would have guessed 79 was the limit before finding the trick.  Now I think it's 74.