recipient preferences

[Tenui]

Hi all,
When I created my key I chose AES256 as the encryption algorithm. When
I encrypt to self (to encrypt a file on disk, for instance) I get the
warning "gpg: forcing symmetric cipher AES256 (9) violates recipient
privileges".

The command "pref" gives me "S7 S3 S2 S1 H2 H3 Z2 Z1 [MDC]". If I use
"setpref", what must I add to this string to include AES256? Also, what
will be the result if I set preferences to "none"?

Cheers
Tenui