Just received Eugene's lovely cyanotype. Thank you very much, its been another successful exchange.
Eugene, when going from an negative - positive - negative, process, one should target the development of the film positive to be slightly flat, with good detail in the shadows, and highlights. By this I mean, if it makes a good slide, you are over developing. You achieve the final contrast in making the enlarged negative. That being said, I have not used x-ray film, so i do not know how good it is at recording the tonal range available.
You mention two coatings, does that mean that you had to re-register the print for the second exposure?