MDC/Non-MDC mode question

[Kahil D. Jallad]

Hello,
	I'm doing some research with gpg and I was hoping someone could
help me with this question:
GPG's default behavior is to use a message digest at the end of an
encrypted message. (The Symettrically Encrypted Data Packet is followed by
20 bytes of hash) At first glance it seems simple to change the
MDC packet to a "normal" OpenPGP Encrypted Message packet since the packet
headers are in the clear, but this is not the case (by design I am sure).