Also, my thanks to Hito. The link you suggested with that tutorial on Gamastutra is just what I need to fix similar seam issues made by the diffuse map.
This is the likely culprit, from what I see here for the center seam at the very least. Proper workflow for baking mirrored stuff: 1. Make sure the entire mesh is there, do not delete half the model and then mirror later 2. Simply offset one side of the uvs exactly 1 unit in the UV view, so they are outside 0-1, this will…