Aegis wrote:

I have looked for a week RE this info, but the great google does not
reveal its secrets to me. Does anyone know what the exact dimensions
are for an "Industry Standard" bolt pattern and the burton 3-hole
patterns?

Industry standard is 4 cm X 4 cm, M6 threads. I presume that's measured
on centre. I believe Burton is a 4.2 cm equilateral triangle.

Neil