florinc:
why do the basic microprossessor boards from all vendors that I've seen not utilize headers that have pins sticking out the bottom so that additional shields can be plugged in under the microprocessor board?
You don't want to plug an LCD or a LED matrix shield "under the microprocessor board", do you?
Why are the headers often shorter (less tall) than the some of the components on the shields?
That's rarely the case. The highest component I saw was the Ethernet connector. You would need to adapt your shield to fit those boards (or pick one that fits).
I've overcome the problem of component height exceeding the header height by simply by stacking a second set of headers into the board with the "too tall" componets. Then use some hot glue to make it semi permanent. The pins still all line up, there is no permanent HW mod required and can be undone at any time; and the next shield to be plugged in (above) the modded one will sit parallel to it, no tilting. I still have to try my idea of desoldering the existing headers from the Arduing micro- controller board and replace it with headers that have pins that could plug into shields below that card. The original headers will be used to protect the protruding pins when not i use. I just have to seal (insulate) the pins from protruding onto any surface and cause problems. Some more hot glue may be in order to accomplish that. Sometimes the problem is asking the question in just the right way. Then the answer then becomes obvious. Thanks for the replies I've gotten on this so far. It's been gratifying to realize that others have encountered the same issues.