Bruce,
I don't use de-humidifiers on my Randalls...and I live in humidity heaven! I'm a firm believer in keeping your Randalls like fine cigars. 70-80% humidity and a temperate climate work well. As I posted a few years back, I have had exotic handles crack...vividly, due to too cold of a temperature. I have also had Colt single action ivory grips "check-up" when there was not an abundance of humidity. Please enjoy your Randall knives...but with "care".
I've seen Mitchell's set up and it is similar to mine. They just plain "work".
Best, Capt. Chris