Possible move for BlackJack.. need help please.

[Puddle]

What is the average EV of a double down? I have figured out a move that takes the house rules and uses it against them. The move will allow the player to do nothing illegal and possible double if not quadruple their original bet. I am looking for a PM from a reliable source. I am not a blackjack guru by any means but I do have knowledge of the game. 6 deck game house stands on any 17 double after splits. except aces(one card each)