I'm going for a record here with stupid questions - I don't have room for slosher trays. Is it just that the top ones won't get even development or that the developer between the sheets gets exhausted?

In other words, what if you put a few "dummy" sheets of already-developed, fixed, and washed film on top to keep the others down?

I know, I could always just do one sheet at at time, but I'm just asking...