Good job on the rack. I have build that exact rack. I have had many problems with the rats chewing on the tubs. I beleive this is caused by the tubs sagging in the front, and them sliding around. I have also had a lot of problems with the middle tubs sagging, so had to install spacers between each rack to hold the MDF up. I have thought of installing runners to hold the tubs up, but it would take a lot of work now that it is alredy built.

Good luck with yours.