Randall, you do have a point on the coin slot on eating them slower. Good one.
As far as the design goes for the inside, I started out with a pattern I downloaded from the Scroll Bench website, which was round shape in design, but I wanted a square shape design instead so I modified mine as such. I also carved out some additional wood that wasn't needed for the structure so I could reduce the weight just a bit. I also had to make my holes a little smaller for when there were two small M & M's trying to come out at the same time and more or less stopped the lever from turning. Also, I used a Jiff peanut butter jar for the plastic container on top. (Yea, I'm now eating a lot of peanut butter).
Here is the url on where I downloaded it.http://www.scrollbench.com/search/label/Free%20Pattern