asterisk users - May 2005 - Grandstream, Asterisk and codec mismatch

Here is the situation. I've got * installed. I have Grandstream BT-100 with
latest beta firmware installed and Cisco 7960G. 

[3710]
; -----------------> Grandstream
context=default
type=friend
username=3710
user=phone
host=dynamic
dtmfmode=rfc2833
mailbox=1710@default
qualify=2000
disallow=all
allow=g729
allow=ulaw

[1707]
;---------> Cisco 7960
context=default
type= friend
username=1707
host = dynamic
mailbox = 1707@default
dtmfmode=rfc2833
qualify=2000
disallow=all
allow=g729
allow=ulaw

On Cisco 7960 preferred codec is G711. Here is a fragment from
sipdefault.cnf

---------------------------------
# Codec for media stream (g711ulaw (default), g711alaw, g729)
preferred_codec: g711ulaw
---------------------------------

On BT-100 in codec list #1 and #2 are G729 and then G711, G723.1 and so on.

When 7960 calls BT-100 then G711 codec is used. But when BT-100 calls 7960
always G711 is used.

My question is - there any way to force using G729 codec when BT-100 calls
7960 with following conditions:

1. without setting G729 as a preferred codec for 7960 
2. without setting all codecs in BT-100 to G729?

 So, is there a way for a outgoing call from BT-100 to use local end's
preference of codecs, instead of remote end?

I.N.