Thanks for all the private responses. I don't have everything needed
for a legal installation yet but I am now relatively certain it is
possible. Neal Pfeiffer was kind enough to put me in touch with
Charles Pate at Cessna's Structural Engineering Department. Charles
directed me to the FAA's Advisory Circular 43.13-2A figure 8.9 which
is online at:

http://www.airweb.faa.gov/Regulatory...visoryCircular
..nsf/1ab39b4ed563b08985256a35006d56af/e533bb05389c90e486256a54006e47b2/$FILE
/Chapter%201-8.pdf

If it wraps cut and paste it as required to make a link. It gives
general guidelines for installing tow hooks on tailwheel and tricyle
gear airplanes.

He also forwarded a document file which described Cessna's testing of
100 series aircraft for towing and how nearly all structurally handle
1,200 lbs x 150% at various tow angles. This document is probably
available on letterhead from Cessna's Structural Department. Allow at
least a couple of weeks if you need a copy. Mr. Pate also sent photos
of an installation he saw in Texas.

The best information he sent were some unofficial copies of the
Javelin Aircraft STC for the tow-hook installation. He said that David
Blanton Sr. who passed away a few years ago donated the tow-hook STC
to the SSA. The STC drawing shows how to fabricate a steel bracket
that connects to the tailwheel using longer versions of the original
through-bolts. It is a very clean installation. I have been told
Gasser Banner can supply the bracket and the Schweizer hook. I have
contacted the SSA about purchasing the STC and Gasser Banner about
getting the Bracket and Hook. Interesting that the Javelin STC uses a
nylon cord running from the hook along the outside of the fuselage
through the pilot side window tied to the "assist strap" with a
specified amount of slack. To release the tow line you pull on the
cord. Seems like a very elegant solution - especially if you only plan
on towing ocassionally.

I hope the SSA has its act together enough to market the STC.
Hope this will be helpful to someone else in the future.