Size of Mounting Nuts

Both Sanwa and Seimitsu buttons are 30mm… however, you cant base art or the spacing of the buttons based on that, because the mounting nuts to the buttons are much larger. What are the size of the mounting nuts? I noticed the Sanwa nuts are larger than the Seimitsu nuts too.

Sanwa: 36mm
Seimitsu: 34,6mm

Also, you can use a Seimitsu nut on a Sanwa button. Just so you know ^_^.