I would put a center dado on the bottom of the cabinet and a coorsponding rail on the bottom of the drawer so that it slides straight. Waxing the rail to prevent binding might help out too.
edit: you could also do 2 dado/rails. Make the rail 1/8" thicker than the depth of the dado. This would reduce friction as you would just be sliding on just the rails, not the entire bottom of the drawer
We put the pins in when I transferred the box to my new rig.dont like the pins in the top, they get in the way and are hard to get out when there is stuff on top. but latches will be in the works at some point