Digging up an old page (I am not sure if the film still has that characteristic curve), Provia 100F had some very nice lack of reciprocity failure. http://home.earthlink.net/~kitathome/LunarLight/moonlight_ga... (from http://home.earthlink.net/~kitathome/LunarLight/moonlight_ga... - its an old frames page).

The correction for a 1200 second (20m) exposure on Kodak black and white film was at 12x (for 14400s, 4h). However, the extrapolation for the curve for Provia 100F put the reciprocity failure for 1200s at 2.35 for a 3000 second exposure.

Looking at the methods and results is interesting, though I've gone nearly full digital now.