I will keep that in mind as far as insulating it. I have a adult rack the same type thats not insulated and seems to be doing alright but Ill look into that for this one.
As far as them popping off the lid you can make it more of a snug fit I just had a cheap saw that wasnt easy to work with and left it as is. Or you can put some panelling underneath each shelf and make it an even fit so you wouldnt need lids. Just was more work then I wanted to do.
Understand that all to well. i would have built my own as well this time around, but the misses wanted to go to pre-fabbed, so 5 weeks later, ( i could have had it done in 3 days), we are now waiting on Fed-Ex.