Actually MDF is weaker than Particle Board(PB). Yet PB is more brittle under stress. MDF is just a better product for painting. The MDF that you find in your local HD or LOWES isnt the same as we use in the industry. There is a product call "TRUPAN" which is about 30% lighter.

I finally got around to pulling the box out and it has already destroyed the carpeted/masonite cover over the tire. Not to mention a tire without a jack . It looks like there are two side pockets in the corner just waiting for a custom fit sub box. Just gotta find the time .....Jack