I am not familiar with the racks from cheap humidors, but a lot of people go with full trays with no ill effect on humidity throughout the humidor.It all depends on what you want to do and how you want it to look. Here's a thread by GolfNut (he makes trays) that show full trays in wineadors:
http://www.cigarasylum.com/vb/showth...=41485&page=12