Hows the homemade meter?
Very good! It's not a proper meter, but a comparator. It basically has a bar graph with a 4-stop total range in 1/4-stop steps, and a sensitivity dial. You plop it on your paper, adjust the graph to some middle value then you can use it to compare brightnesses for changing between print sizes. The photodiode is a very small point so it's easy to compare using say, someone's forehead.