How to filter the Camel CXF header when the dataformat is MESSAGE?

Issue

In production we have an issue whereby our F5 is stopping HTTP requests because the headers are over a configured threshold of XX Kb. to resolve this, i am attempting to configure my CXF client endpoint as per below. but when executing locally with break points and logging I am not seeing the header filter strategy being executed. The Camel CXF headerFilterStrategy not being invoked.

<bean id="cxfHeaderFilterStrategy" class="org.apache.camel.component.cxf.common.header.CxfHeaderFilterStrategy">
    <property name="messageHeaderFilters">
        <list>
            <bean class="com.redhat.testcamel.ws.CxfHeaderFilter" ></bean>
        </list>
    </property> 
</bean>