BuddyPress.org

Since you’re using the filter I posted, I would manually setup a group loop. Then in this loop, I would use the bp_core_fetch_avatar() function with the “html” parameter set to false (view the full function and parameter list in /bp-core/bp-core-avatars.php).

Doing this will return the URL of the avatar, then you can manually define the width and height in an IMG tag.