OK... I am AGAIN having issues understanding what size drawer I should be making for the Blum Undermount Drawer slides. I have three different lengths of slides and I believe the drawer length is equal to the slide length i.e. for a 21 inch drawer slide the outside dimension of the drawer (front to back) should be exactly 21 inches. What I appear to be struggling with is the outside dimension of the drawer width. I am building boxes with face frames and inset drawers. The drawer material is 1/2 inch prefinished plywood. I am padding out the slides to be even with the face frames. So if the inside opening (width) of the face frame is 32 1/2 inches, what should be the outside dimension (width) of the drawer box.