If you were getting mold it was just too moist inside that humidor. Same thing happened to a very expensive box of cigars I got once. After that point. I would just take a napkin... wet it... then squeeze it out extremely hard. So that the napkin didnt even wet my hand when I grabbed it... almost was on edge of dry. I found this was perfect level of moisture. I am sure the amount of moisture you have to have reflect the amount of space.
Frequent inspection of the contents is key. As you have to keep the moisture levels right. What amazes me is that puerh is stored in caves. I cant think of a more moist, dank and moldy place. I suppose the caves they pick are a perfect balance of moisture and conditions.
While I dont know much about purerh... I can say confidently that if you can store puerh in your house without getting mold. I would use your meter to measure what the average moisture is in your house. I would try to aim for that inside that humidor. You just mostly want to avoid spikes (high or low spells) that you would normaly get by storing it in your house.
Shogun read this website... should all be directly applicable to helping your work out the kinks. Hope it helps.
http://cigarhumidors.vigilantinc.com/ci ... -101.asp#1