That's why using a high res camera to image the entirety of the spools and make adjustments as necessary seems like the best way to close the loop. It won't be

That's why using a high res camera to image the entirety of the spools and make adjustments as necessary seems like the best way to close the loop. It won't be able to make minor adjustments but if something is really wrong it wouldn't be hard (algorithmically) to locate which spool is totally bonkers and get it much closer to right.