EOPrototype help

I have an application that was build on FrontBase and I am trying to 
make it work with Postgresql as well.  Using the same eomodel file.

As near as I can tell I need to mess with the EOJDBCPrototypes from our 
current eomodel file and adjust them for Postgresql.

SO...
Existing eomodel file uses EOJDBCPrototypes for all entity attributes.
The prototypes only define the Value Class, External Type and Width 
where applicable.

What I'd like to do is override the EOJDBCPrototypes at application 
startup, depending on which database is being used for that particular 
instance of the application.

This is where I get lost.  I can't seem to find any documentation about 
how to override this (in the WO 5.2.3 documentation, google search, 
omnigroup etc.).

I found something about creating a separate framework with your 
prototype and change the framework you use for each database...  seems 
a bit much to me.
I see in the documentation that I could, if I wanted to, create the 
whole eomodel in code.  That leads me to believe that I should be able 
to create (or at least set) the prototype that is being used depending 
on which database is being used.

Except I can't figure out where to do that...

sim