young chin cage help

I have an adult chin but will soon be having 2 young sisters (not in the same cage). I have done some research and am getting mixed messages. Some are saying they can go in an adult cage with ledges while others are saying that they should not have higher jumping ledges than 12-18 inches until they are about 8 months old. I dont want to put my new babies in danger so am thinking of just taking out the top shelves to limit their jumping height but how high can i put shelves and until what...

young chin cage help