Acoustic Guitar Construction

I keep my humidity in the mid 40s. I have to say I would not worry as much about building in the 30s as I would building in 60s. When guitars expand in high humidity, the setup goes to hell, but the guitar generally survives intact. When the humidity drops below 20 which often happens in home in areas where there is a cold winter, the backs and tops crack. The doming we put in the top and the back give the guitar a bit of safety from low humidity. Still in the midwest when the temperature drops to the teens or less repair shops get a lot of business.