Deploying Rails app on existing Apache server

I have developed a new app using Adobe Flex as the front end and Rails
on the Back end (no html). I need to deploy to a Windows 2003 server.
I have decided on Apache 2.2.4 and Mongrel clusters.

I have setup a test environment on my own PC using Win2k, and have got
it working, i.e I have proved that I can have 3 mongrels running and
be serverd by apache.

This is the relevant section from httpd.conf

<Proxy balancer://wibblecluster>

<VirtualHost *:80>
ProxyPass / balancer://wibblecluster/
ProxyPassReverse / balancer://wibblecluster/
ProxyPreserveHost on

the wibble is just my own test name.

I have not used Rewrite Conditions or Rules, which I assume means that
all requests to Apache get passed to 1 of 3 mongrels.

My question is what is the simplest way of getting only my small app
to be served by a mongrel, and everthing else by Apache directly.

I just came to Apache and don’t really understand the rewrite stuff.
Would it be easier if I had all of my app in its own sub directory
such as /myflexapp/