If you are using large or even medium format and you think your shadows are too dark, give them more exposure. [Same with 35mm except you worry about grain.] Don't place something at under III if you want it to have detail. There might be some detail there with some films, but generally you aren't getting good separation or detail or local contrast until you get well above III. I know that I don't worry much about what is under III. I place my IVs in most scenes and let everything else fall where it may. In some unusually dark scenes, I check the IIIs and IIs, but not much.