I think my buttons probably are spaced apart more than a lot of cabs I've seen on here.
But I made some cardboard mock ups and tried em out and went with what felt comfortable to me.
The cab is 19.5" wide, 33" at it's deepest point and 66" at its highest point.
The rounded part on the front of the CP was done with a router, another I idea I got from Paul (mini Space Invaders).