Replacing the XML parser in JRE 1.4&later

Hi,
We have a client/server application running on Tomcat with JDK 1.4 and 
web clients with JRE 1.4 or later. We recently merged to JDK 1.4 ; 
before we were using JDK 1.3 with JAXP and the Piccolo parser. As 
parsing speed is crucial to our application, we want to keep Piccolo. 
How can I "replace" the included Xerces parser in JDK1.4+ with Piccolo?

Thanks in advance,

-- 
Jimmy Monin
Development & SCM
EADS S&DE