air flow on a rack question

I'm attempting to plan out a build for a rack.
Would it be better to leave a small space for air between the tubs and the shelves or solder holes into the tub itself? Or is there no need for either?
How would the humidity for any of these options be affected?

I have no building experience, so bombard me with your knowledge!!

Thanks!

I've built a couple of my own racks, so I'll chime in.

First thing is that you'll want a little space between tub and shelf, or you'll have binding issues. For hatchling tubs (6 qt sterilite) I use a single cd on each corner, for juvy/adult/breeder tubs (12-15/28-32/41 qt tubs) I use 2 cds on each corner. This allows a little air flow room and enough to keep the tubs from being a pain to pull out/push in.

I also always use a soldering gun and put either 6-8 holes in front and back of tub and 5-10 holes in the long sides. Just remember about holes, it's easy to put more in, a little harder to take holes away, so at first don't go overboard.

Also what kind of material are you building the rack out of? Are you going with solid sides and back, or just "legs"?