As in http://tools.ietf.org/wg/secsh/draft-ietf-secsh-filexfer/draft-ietf-secsh-filexfer-13.txt.
Not going to happen, sorry. The filexfer standards jumped the shark after version 3 of the protocol and we decided not to follow. We have added protocol extensions for certain things that are missing from v03 that are present in later drafts and are willing to entertain more, but we have no desire to implement everything.
Close all resolved bugs after 7.3p1 release