can h2 extension frames carry data?

Hi folks, I have a simple question: can HTTP/2 extension frames be used to
send data?

In draft-kerwin-http2-encoded-data I've defined the GZIPPED_DATA frame,
which is just like DATA but gzipped. It's protected by a setting which
defaults to 0, and you MUST NOT send a GZIPPED_DATA frame unless the peer's
setting is 1.

The problem I'm facing is, what happens if a buggy peer sends the frame at
the wrong time (or, potentially worse, if a buggy peer sends the setting
incorrectly?) Because "implementations MUST discard frames that have
unknown or unsupported types," we can end up silently losing data, with no
way to detect it, let alone throw an error or recover.

In HTTP/2 we've been pretty good at backing up most MUST NOTs with
detectable errors, and I don't feel comfortable introducing something where
the "or else" is "the page you requested/sent evaporates silently."

Is this a deficiency of HTTP/2's extensibility model? Or am I missing a
simple way to make it work?

Cheers
-- 
  Matthew Kerwin
  http://matthew.kerwin.net.au/