The time has come to build a horizontal enlarger for negatives up to 8X20. I have purchased an old 16X20 process camera and am looking for guidance on selecting a light source. I'll need to build the enclosure for the light and get a piece of opal glass for diffusion. Also, do any of you have suggestions about building the glass sandwich for the negative holder? I was considering something along the lines of the type in my Durst 138 but didn't know if Newton rings would be a problem. Thanks in advance for your ideas and shared experience.