Harvey,

I chose to NOT hook it up according to the STC for the
430W, so GPSS is NOT disabled when the CDI is switched to VLOC.

Not many of us have that option. You're flying an experimental.

It is
because my autopilot flies like a pro with roll steering but
in NAV mode and following the needle, it S-turns like a drunken sailor.

Not many of us have that problem. You're flying an experimental.

gd&r

What I'm trying to say is: If the S-TEC installation is properly done in
an aircraft it is designed for, it will follow the localizer in approach
mode just fine - and it'll be the legal way to fly that approach.

--
Thomas Borchert (EDDH)