XML Commons Resolver and large data URLs

In Apache FOP, I've just run into a small problem. I got an FO file with
a rather large data URL (RFC 2397) in it. If I hook the Commons Resolver
into FOP it takes ages (CPU at 100%) and all get get back is a
TransformerException from CatalogResolver.resolve(String href, String
base) telling me "unknown protocol: data" which is actually expected if
someone tries to create a java.net.URL and no protocol handler for RFC
2397 URLs is installed (Note: We're supporting these URLs natively in
FOP).

Is there anything I can do in the catalog to shortcut this or would it
make sense to simply ignore all URIs which start with "data:" (i.e. they
bypass URI resolution)? The latter could be done in either FOP or
Commons Resolver but doing it in Resolver would take care of the problem
for all times. I don't think anyone is going to rewrite RFC 2397 URLs.
Or is it expected that a RFC 2397 protocol handler is installed when XML
Commons Resolver is to be used? Any comments?

Thanks,
Jeremias Maerki