OK. Well I managed to figure it out myself.
According to the documentation, during installation of the OWA extensions, the installer looks for the highest number control folder that exists (and is supported) in C:\Program Files\Exchsrvr\exchweb and installs there.
However this has not been the case for me. I installed and uninstalled twice. The installer insisted on putting extensions into an older folder, even though a higher numbered folder that is supported by the version I am using did exist.
What finally worked was:
1. Remove the extensions (cscript Frontend2003Setup.wsf /remove) and then an uninstall via Add/Remove.
2. Renamed the directory to which extensions were erroneously being installed.
3. Reinstall the extensions and verify the correct controls folder was modified.
4. Run the setup script via the shortcut or by hand.
5. HUGE SUCCESS!
And just for the record don't try install them by hand. That gets *REALLY* messy.