I'm currently in the process of building my guinea pigs a new cage. I've decided to go with a cage consisting of three 2 x 4's on top of one another. Half would be for the girls and half for the boys. I currently have the first and second level built but I have stopped because I feel that it is not very secure. I am leaving the front row of grids off so that I can make a door to each level. Can the first level support the second and third level without it having the front grids for support? If not, then what can I do to give it more support? On the second level there is a row of grids splitting it into two 2 x 2s. Thanks.