Maximum height correx sides?

[Black piggies]

Just built the piggies a new cage (again), 5x2 c and c. Somehow the correx sides are super high and I'd never have a hay mess problem again if kept it like that.

What's the max height the correx sides can be for them to get enough fresh air etc? Meantime I have cut them a couple of 'windows'..

 

[KathT]

I make my sides 15cm all round and although a bit of hay occasionally gets through, it’s mostly clean.

 

[Reenie]

If there's no top (or only a grid top) on the c&c it shouldn't matter how high the sides are, as there will be plenty of air.