In FIVB Offical Beach Volleyball Rules 2017-2020, which rule allows for a double contact while using an overhand finger action on a hard driven ball?
I see an exception for Extended contacts:
220.127.116.11 Extended contacts: In defensive action of a hard driven ball, the ball contact can be extended momentarily even if an overhand finger action is used.
The only information I found supporting the double contact was from the 2015 Beach Volleyball Rules Casebook, case 5.3.11 (5.20)
5.3.11 (5.20) Is it allowed to play a ball as a hard driven ball (i.e. by momentary extended contact with hands) if the ball is coming from the opponent’s block? Ruling
Answer (emphasis mine)
Yes. This is legal if satisfying the requirements of a hard driven ball defence. The ball rebounding or being deflected off the block is considered as an attack hit and in this case the ball may be caught momentarily with hands. It may also be double contacted with fingers. Rule 18.104.22.168