120 pop rivet dimple die

So I don't have this item. Is the only place it is used for the closeout tab on the left elevator?

I looked at the online listing for the Avery pop-rivet dimpling tool - the tool that uses the hand riveter to dimple. It says it is fine for 120 deg flush rivets?

Any experience here to keep me from having to buy a 120 deg pop-rivet dimple die?

I had a similar question here. http://www.vansairforce.com/community/showthread.php?t=107110

Thanks! Buying the die?.