Add more holes to the tubs, I have sterlite 28qt tubs & each tub has over 200 holes in them here are some pics
http://i165.photobucket.com/albums/u...ub100_2383.jpg
http://i165.photobucket.com/albums/u...ub100_2381.jpg
Start with the holes you've made, then keep adding until desired humidity level is reached. A soldering iron is great for this.