1" mdf
have you checked home depot/lowes? if they dont have any ask there where you could find some, they DO make it, its usualy a commercial material (used for commercial businesses)
3/4" is strong enough for any man. Saves some weight, also. The key element in a strong system is the joints. Predrill, use lots of screws, and glue the heck outta it. Make sure the edges will fit nicely. It'* all in the joints.



