First off, let me just say your cabinet designs shown in the photos are beautiful. I am very impressed.
The definitions for Door/Drawer Front Top Clearance and Door/Drawer Front Bottom Clearance parameters can be found in the User’s Guide on pages 320 & 326 for Base and Upper Cabinets respectively. They only apply when there is no Top or Bottom rails.
When CabWriter first came out it did not support overlay door/drawer front designs. Hence, the Base Drawer Front Heights matrix on the Face Frame tab is inset drawer front centric where the drawer opening minus 2 x gap is the drawer front height. When we added overlay support we made the drawer front width the opening width + 2 x overlay distance and the drawer front height the opening height + 2 x overlay. You can map this back to the Base Drawer Front Heights matrix with your equation, though I don’t know why you included the 1/2″ desired reveal. That comes into play when you calculate the top, bottom or mid rails.
I suppose in CabWriter 6 we could provide separate parameters for the sides overlay and the top/bottom overlay. In the mean time you could either use 3/4″ to 3/8″ overlays, or manually change the vertical overlays with native SketchUp tools. That’s the best I can offer now.
Greg, can you add any comments?
BTW Michael, if you want to carry this discussion further you can call me on my mobile: 413-961-9115.