with my IIS7 site, i manually set the bindings for my site. Here’s an example screenshot.
Is it possible to set these bindings in the (local) web.config file? Not a machine or app config file … but the web.config file?
Cheers 
You cannot. The system.webServer settings are supposed to be stored in applicationhost.config file only. web.config can have site specific changes or modification but Web site specific configuration are always stored in applicationhost.config. are element and are in turn element.
From IIS 7 Resource Kit:
ApplicationHost.config contains
configuration sections and settings
that only make sense globally on the
server. For example, it contains site,
application, and virtual directory
definitions in the section and
the application pool definitions for
the section.
Check more discussion of this question.