Just exploring something here. When I serviced my wife's bike, I was able to set the height of the front mech cage relative to the big chainring. I think the Zinn book says something like 1-2mm above the teeth. On my bike however, there is no way I can see to adjust the height of the cage as it is a rigid construction that fits onto the bb. I can't see any screws on the cage that let me adjust the height.
So, what do they do with chainrings of a different size? For example, my chainrings are 22-32-44. If I fitted a different set of ratios then would the cage height no longer be compatible with the new set? Or do you have to replace the front mech at the same time with a version that matches the new chainrings? I know some front mechs of the same model have different tube diameters, but I've not heard of one that has a different cage height.
I'm not replacing my chainrings, but I'd like to know more about this if you can help.
Edit: I forgot to mention that the cage height above my outer chainring looks to be something like 6-8mm thereabouts, and I'd like to correct that but can't see how.