totallytentative

I think read about taping the sealing lip on the lid so that you reduce any gaps, but I can't recall what type of tape to use (or indeed, what sticks to wood well). I don't imagine it'd be something super thin like cellophane tape or "magic" tape because it wouldn't make enough difference.

I should find out one of these days because I have the same issue with a smaller (and admittedly cheap) humi myself.