Vertex slot question

I was considering CNC machining the Mendel vertex part in two halves and sandwiching together. My question is; can I change the two holes that go through the sides of the part to .312(5/16)? I have a ball endmill that will work well if I do it that way. Also,the teardrop profile that you see on those above mentioned holes, is that really necessary or is it just a quirky place to put the Reprap logo? Thanks in advance for any help.

:-D
My guess is that the reprap logo is invented from the vertex part ;-)
The terdrop shape is because the piece is designed to be printed on reprap and with reprap you cannot 3D print parts that are "hanging on the air".. actually 45 degrees walls are possible -> holes are teardrops ;-)

About your original question; the hole is designed for a 8mm threaded rod. There are nuts that fastens the rods, so making a little bigger holes might not cause troubles. Try it, you'll see..
There are others using cnc to make the vertex parts, for examle, see this:
[finreprap.blogspot.com]

You don't even have to use a ball mill. I use an end-mill and make square slots. It holds every bit as good as the original.

As far as 8mm vs 5/16... you shouldn't notice but you could slightly deeper to adjust it. The material, unless your milling metals, will compress enough to compensate.

Thanks for all of your input. I am going to be making these today. I will hopefully have a couple of sets up on Ebay next week. Thanks again!