picked up a cat litter pan(another question)

[Mark]

I picked up a pan that I'm hoping will work for 1.3 rats. I woried about it no sliding onto a rack well since the sides are made so that they have a slight curve(enough so that is may effect how much of the lip can be held. Does anyone else use pans that are not a perfect square. Also the floor area of it is 18.5"x12" width a 6/5" height. THe top demensions are 22x16 from edge to edge. It seems it would be crowded with (4) 200-400grams rats in it but I may be imagining it. any help would be great.