Basically winged it... I traced the original onto MDF and used a Capcom Street Fighter II template to position and drill the controls. Its a standard 6 button layout, the 6th buttons are hard to see because they are black.
If I was going to do it one last time, I'd eliminate the separate mouse buttons, and use them as the bottom row of player one.
Almost forgot...The one mod I made as far as the layout was putting a thumb button by player 1 stick for Defender. I just eyeballed that one. If you want the Capcom template and can't find it, let me know and I'll send it to you. I think I found it here by just doing a search.