[ESS] overriding <tab> in noweb-mode

[Bill Rising]

Hey folks,

This is really dopey, but I'm ripping my hair out trying to override  
the <tab> in the doc mode. It seems to be permanently set to 'noweb- 
indent-line, regardless of which of the hooks I try to add to.

How can I reset shift-tab to noweb-indent-line and let the doc mode  
use its own definition of the tab (which is set in its own hook)?

thanks,

Bill