How to remove unnecessary "xmlns:xx" attributes?

I currently have an ad hoc Soap client framework that uses JAXB to
marshal a Soap request.  This generates a "minimal" Soap envelope, in
that it contains a "xmlns:xx" attribute for every "xx" that is actually
referenced in the request.

The WSDL that defines this request references numerous schemas, and
defines all the possible operations for this service.

I'm now doing an experiment to see if I can replace our ad hoc Soap
client framework with Apache CXF.  My results so far are ok, but I
noticed that the request that is built now contains "xmlns:xx"
attributes for EVERY schema referenced in the WSDL, even if that
namespace isn't referenced in the request.  As a result, my requests are
now 20 times larger.

I'm examining whether it's possible to get back to what I had before,
although with the new framework, but I think it may not be practical.
I'm not even sure the resulting larger request will result in any
increased latency.  It might make no difference, from a performance
point of view.

However, these requests are occasionally saved and passed back and forth
in email, to discuss certain operational issues.  It would be ideal if
these requests are "minimal".  If I can't solve this problem at runtime,
I'd at least like to have an XSLT stylesheet that can "minimize" the
request by simply removing the "xmlns:xx" attributes where the namespace
referred to by the "xx" prefix is not referenced in the request.  I've
googled about this, but I haven't found a clear solution for this.  Does
someone have an idea how I would write a stylesheet to do this?