Bulkhead Alignment: Going Slow

Started aligning bulkheads today. I thought this would be tedious and I was right. I gave up on having a transom with no holes as I quickly decided I needed a reliable way to anchor my line I thought would help in aligning the bulkheads. I built up a frame for the transom and then aligned BH6 to that. It took a bit too long to get BH6 plumb and level. I just started on BH5 but can't see the mark on the transom through the alignment holes (lower set) so I don't know which way to move the bulkhead.  I'm going to get a laser pointer to see if I can figure it out that way.  I think the crux of the difficulty besides building in a shed that is sitting on gravel is that you need to simultaneously move things and have them stay put. Here is a picture, I was shining my light on the transom to try to see if it helped my ability to see the lower alignment hole.