We did some modifications to our CIM-U-Lator plates this evening to aid with ventilation. I've uploaded the Working Drawing and part files (Both in Inventor 2012) to illustrate the changes we made.
The Working Drawing has the necessary coordinates for the tool path if using a mill capable of moving along multiple axes simultaneously. If using a purely X-Y mill, the 45-degree angles on the slots allow for the plate to be machined by turning the vice on a 45 and then machining straight through
On the face of the plate, you can open the blind mounting hole with an eighth-inch bit. You can then tap through and use 3/4" Bolts to connect the plates, allowing for greater engagement and avoiding the possibility of bottoming out the threads.
EDIT: Thanks to Andy Baker for the inspiration. The modification is similar to that done on the AndyMark Planetary gearboxes.
EDIT 2: Sure enough - the .ipt of the CIM-U-Lator plate that I used for this print had holes in the wrong location. Everything should be resolved now. The idw is attached.
EDIT 3: I've uploaded a .pdf of the working drawing for anyone who'd like the drawing without having to use Inventor 2012 to open it.