serving WO app through a proxy server

We have an interesting problem to solve.  We will be deploying an app which
will be accessible only through a proxy server.  This means we have the
following transformation to deal with:

http://foo.com/BAR/cgi-bin/WebObjects/app.woa
will wind up hitting the following on our side:
http://mycompany.com/cgi-bin/WebObjects/app.woa

this is not that big deal, since the proxy works quite well.  The problem is
that any dynamic urls never point to the right place.

They point to :
/cgi-bin/WebObjects/app.woa/wo/hLxVZzguPp0ZTc4kBe9lQ0/0.0.2.1.1.0
instead of:
/BAR/cgi-bin/WebObjects/app.woa/wo/hLxVZzguPp0ZTc4kBe9lQ0/0.0.2.1.1.0

I've tried setting the WOAdaptorURL, but that only delivers the correct path
on the first page.  each subsequent page is missing '/BAR'.

How do I tell my app to look for apps using /BAR/cgi-bin/WebObjects as a
prefix?

Thanks.