well, this may or may not be helpful but...

i had a lot of concern for humidity during the winter up here too, and came across a few letters and articles here and there, most notably at Charles and Margaret Baker's site, that talked about the inaccuracy of hygrometers/humidistats and using their readings as benchmarks instead of taking them literally. my meter has had the occassional reading that, if correct, should have been high enough to rain in my livingroom.

as i'm sure you know, it can be tough around here to get that much moisture to stay in the air this time of year; i let the humidifiers run and play with the heat and fans to make adjustments - a couple weeks ago, i had a day or two that it was damp or clammy as opposed to humid, if that makes sense, and bumped the heat up a bit to spread the water in the air out. besides how it felt, the best indicator was the plants - a couple of my stan's leaves developed a spot or two. not a really high price to pay to learn what it's supposed to feel like, for me anyway. an aeranthes is now spiking, a good indication for me that the mix is about right...good luck with it.

p