If you watch the top flankers today, they have their arm across the shoulders of their 2nd row. (Which sounds more like the former.) We need to remember "When a player binds on a team-mate that player must use the whole arm from hand to shoulder to grasp the team-mate’s body at or below the level of the armpit." (law 20.3)
I also suggest it is important to avoid resting your outside hand on your props leg, as I have had some players do.
Keep an eye on the ref, if he's not watching, don't worry too much about your bind, just don't break too early cause that's a dead giveaway. I'm not condoning cheating here, but its commonplace in the professional game.