Humi in a Humi

I would say you best solution is to drill a hole in the side of both the smaller humidor and the cabinet, then seal in a flexible PVC tube between the two. Then, from within the cabinet, point a fan at the tube hole to circulate air from the large to small humi. You may have to repeat this process for an "air return" as well. Finally, you will have to anticipate a "humidity lag" of approx x = (( 10% X volume small humi / volume large humi ) X length of tube (cm) / 2.75) X diameter of tube^2 X 3.14144 / 100. Thus, you will want to set the large humi RH to y+x, where y is the RH you want for the small humi.

Cheers

John