Some time ago I found reciprocity failure compensation numbers for Fomapan 100 film [aka Arista EDU Ultra]. This emulsion is notoriously bad at handling long exposures. “Murray@uptowngallery” on APUG simply took the three points noted in the official guidelines from Foma and plotted out all the seconds in between. So far they’ve worked for me. Perhaps they’ll work for you. I’ve set it all up on a one page PDF.