I can reproject them to mercator type as long as the curvature is not too great so that would be easier nearer the equator. It would not be exact (as its doing a limited power curve fit) but it would be darn close. I was asking because I tried to stitch them together as is but they would not line up exactly due to the projection and again its harder nearer the poles. So I thought before I go off and try to get them squared up into vertical and horizontal grids it might be easier to ask if you have that capability. Once its square then its easy to get the grids to match and I can see that your software is definitely doing georeffing so I can tell that its an exact match under those grid lines. Id like to see this map stitched into one large array so ill take a pop at it. Its a bit tricky but I think it can be done. Its just awesome. God knows how many hours you must have been at it.