ProfMac: There are 4 modules with 8 units each. Module 1 has unit 1-8, module 2 has unit 9-16 etc, module 3 unit 17-24, module 4 unit 25-32. So module 29 would be the 5th unit in module 4 if I'm not mistaken? There is numbering on the silkscreen of the back planes, so it's easy to see.