One other thought and this again may be of no use to you but have you considered using a chrome film inside your camera and then you could scan or make prints from that.
Or for that matter color negative film.
Neither of these are nearly the same as using color print paper as the "film" of course but I suppose using a chrome film would still let you live in the realm of odd color shifts due to the long exposures.
Would the color sensitivities give a print that is more saturated than a negative of chrome?
I've read that papers resolve about 50 lpi, is this about correct?
If so, particularly for a 8x10 pinhole that I could enlarge to 16x20, a paper negative might do quite well.
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