Custom cages

[Trollbie]

My dad agreed to help me build a cage for Zeus, but my mom (who told me no snake is ever allowed in her house and wanted nothing to do with it when I got Penelope) is now insisting that we build 2 that are the same size and stack on top of each other.

What size should I make them if one is for a milksnake and the other for a BRB?

Also, it looks like the best opening is one where the glass part opens towards you, right?

Any suggestions will be much appreciated.

And sorry if there already is a thread like this, I know it annoys some members when there's multiples, but I have pretty bad ADHD and searching just gets too overwhelming for me...