Bryan,

Tried the edit you suggested (setup/index.php, include_once changed to
require_once on the Smarty.class.php), unfortunately same result on the error.
Somehow it still thinks Smarty has been declared.

Maybe I'm missing something obvious? Any files I should be deleting between
attempts?

The setup.conf.php remains empty on the attempt so it appears that the process
never gets to that step (that's probably obvious with the Smarty error, but I'm
not looking at the code right now...)