I have to build 31 drawers and install them with Blum undermount slides. The drawers are inset with 3/4" fronts. The back of the cabinet to the front of the face frame measures 22 3/8". I've looked at the specs for the slides and it looks like I need 21" slides. According to the specs I need a minimum of 21 7/8" inside cabinet depth. However, it says for inset applications I need to add the thickness of the drawer fronts to that. If I do that it comes out to 22 5/8", which is 1/8" more than my interior depth. If I go with the 18" slides it says the maximum interior depth I can have is 20 9/16", if I add my drawer front thickness to this it comes out to 21 5/16" which in my case is too small. Am I missing something here? Should I use the 18" and put some blocking in the back? Any help or suggestions would be really appreciated.