Is Content-Length a valid SIP header to screen against in HMR

All,

 

Is Content-Length a valid SIP header that can be screened against within an HMR. I am working on a 4500 6.3 code box, tested also on 4500 6.1.

 

I am running this HMR just trying to see if the box can key on the header field Content-Length:

 

ROCNY11-SBC-A2(sip-manipulation)# show
sip-manipulation
        name                           cl-manip
        description
        header-rule
                name                           Content-Length
                header-name                    Content-Length
                action                         delete
                comparison-type                boolean
                match-value
                msg-type                       reply
                new-value
                methods

When I use the same HMR for Contact the Contact header is removed from all responses. Is there something that needs to be done to the box to enable Content-Length to be recognized.

 

Any help is appreciated.