One of my three girls will be delivering w/in the next week (from what I'm guessing.) Their cage is a 2x4 on the main level w/ 6" sides of coroplast. The upper level is in the shape of a U w/ 1x2 on each side and a bridge connecting the two. My question is this: Should I make the bottom level higher than 6" to prevent the babies from getting out or is this high enough? My bridge and ramp have sides to prevent Angel (my blind girl) from falling off but I don't have coroplast on them and they are made from the grids bent.