After weighing the pros and cons for a while, I drilled a 1.75" hole in the fish box walls. It's right under the striker for the latch in the photo. The change was apparent overnight. No condensation dripping from the lid. No gurgling sound when the lid is stepped on. Everything seems very dry even though the weather is still cold and damp (snowing this AM!). I'll seal the edges with epoxy and call it another successful although small modification.
