Received quite a few posts in response to my query. Since this is not an
issue easily summarized, I'll simply state what I have learned.
The 'L'-shape design (pier and pad) is an actual engineering form. The
shape IS used as I assumed it was... to provide additional opposition to the
overturning moment. My non-enjuneering skool background (deductive
reasoning) tells me that the toe function could also be achieved through an
'inverted'-L design --- a "T". If re-inforced, a "T" design would offer
some additional opposition to the overturning moment (in comparison to the
simple straight-sided rectangle)... although I believe the efficiency would
be much lower this way.
Digging a hole of the "L" shape would be physically impossible for me. LXC
raises the point about safety, too.
Gene's info about the bearing capacity of clay was appreciated. The old
farm (on which my house sits) has a good clay base down about two feet. I'm
going to *assume* that my soil is similar -- I'm never going to get to the
49,000 pound stage.
The comments about an extra $75 being enough to kill a project are valid.
And I'm not able to spend $28,000 on my tower. (unless I hit PowerBall last
night!) So I -- as I assume MANY others are -- am forced to reach a
compromise between doing *everything* the correct way (e.g., "shoring up the
hole", soil analysis, etc) at higher cost and "just enough to get by".
Thanks to ALL for their input.