limelight + content-length & content-encoding

we're starting to test some apps with limelight (a cdn) and it requires certain headers be present so their system will cache content. i'm trying to adjust missing/incorrect headers on outgoing http responses to include content-length and content-encoding.

 

 

* content-length -- from what i gather this header is not returned for dynamic or chunked content. is there a way to get this added through an irule at all? this is my biggest issue right now.

 

 

* content-encoding -- this is inserted via the http profile (as long as gzip compression is enabled) however it seems that the f5 does not compress all responses. is there a list of criteria that a response must meet to be compressed?

 

 

any tips on using irules to help content be cached by an external cdn would be greatly appreciated.