I've got the mixing tubs in my DFN. I didn't have to cut them down at all--it was a tight fit, but it worked. I used to have two tubs (because I had two different groups living in the DFN that didn't get along), but I now just have one tub on the bottom and opened up the middle section of the cage. I had to remove the top part of the DFN to remove the second "floor" (with the cut out, where the ladder/hook is) that separates the two levesl. I added in another homemade shelf to make sure they've got enough floor space and make sure I've got lots of hammocks. It works great for me! Let me know if you'd like pics!