Is my new rack workable?

I just built a new rack that I am going to keep snakes that are over 1000 grams in only. It is already built and wired and everything is done. I certainly am not going to take it all apart and build it all again so I am asking if it is ok or do I need to make some modifications.

The previous rack I made I used 1 CD as a spacer and ended up with a few levels that were a little too tight, so this time I used 2 CDs. No problem there.

However, what I did not notice until now, is that the tubs' upper part aren't exactly a straight line. The left and right of each tub is higher than the middle part, this it forms a slight "U" shape against the wood. It is very subtle and not noticeable until it is against the wood top. As a result of this, there is a 5 inch area in the middle of the front and back where there is a bigger gap between the tub and the wood. The gap is 3/8 of an inch.

Is this ok? Obviously the snakes can not get out of it because the rack will only be used for 1000+ snakes. But I just wonder if this can be an issue.

PS - I just noticed something really weird. Although the tubs are all machine made and are the same model of tub, and look exactly the same to the naked eye, it seems that they are slightly different in height each! When I first tested the rack, there was one level that was a little tight, but today I tested again and it wasn't tight. Apparently the tubs differ in height by a 1/16 or even 1/8 of an inch! When I put one of the "taller" tubs in one of the looser slots, there is much less of a gap. There is still a gap though as the middle part is lower than the edges on either side. I tried with the taller tub and the gap is such that I could not stick a cigarette into the gap without squishing it just a little bit.

I don't see a problem with the rack. What kind of tubs are you using? I know people who's rack doesn't have any space between the top of the tub and the shelf and some who has a small space. Good luck with it