they should be opening a menards by me soon, i'll be on the look out when they do. With melamine prices going up each year, I think its over 40 bucks a sheet near me, I'll spend the extra few bucks for some plastic. Cheapest I could find any rack building plastic was over 100 bucks a sheet last time i looked. thanks for the heads up.
OP to get the right height for your rack, you can cut the sides, and put the bottom piece on. Then place a tub with a spacer (a lot of people use cds for spacers) on it, place the next shelf on top then screw in place, place the tub and spacer on the shelf you just put up, next shelf on top, screw in place, repeat...
Any other option i know requires a table saw to be easily done.