It's busy, but here's something to consider. The switch examples show the center-to-center spacing of the combinations (might not be exact). The blue loop is O54 and the orange loop is O42 (except the bottom Ross example). The green switches show the spacing on the other sides. The inserts show the different look you're going to get with various combinations. However, by adding some custom cut fillers between the switches in the GarGraves example, you can achieve a more concentric look with about 6" of clearance.
