I'm late to the table here, but you do indeed need to allow some margin for reciprocity.
So give your exposures a bit more time for that...especially if you are shooting in shade or indoors.
As far as shooting chrome, it shifts a bit to the blue IMO-- but each film brand has its own quirkiness when it comes to that as far as color goes. I shoot Kodak since in my use it seems to shift less than the Fuji. I also use expired films that have been in the fridge so that also comes into play but not much in my experience.
Print film is not so shifty, but I always find the shift is interesting and adds to the overall pinhole "look".
Most of the time I just pretend to "be" the emulsion or paper and do it by when I think the film has had enough light. I don't count or use a watch anymore, I just do an Obi-Wan and stop the exposure when I feel it's done.
Sounds crazy, but it's what I do.
Love your shots, and hope to see more soon from your next adventure.
Astro
Hope this helps.