this is going to make you sick. I bought a 25 sheet 8x10 tp box at a swap meet for $5. it did have a big dent in one quadrant. So in that quadrant the gelatine is thinned, so less neg density at the crushed spot in the same spot on each sheet.

So I now have about 72 sheet of 4x5 tp that are great, and 22 or so with a known fault. I use them as a second exposure when the development time is in doubt. Develop the dud sheet first, confirm results, and them proceed to develop the keeper.

I also have ideas about how to use the dud sheets in image manipulations for pan masking for mf c-41 negs that are too contrasty to optically print using ra-4. As long as you accurately position the 6x6cm frame, it ends up no where near the optical fault.