Liberal/aggressive doubling under DDR?

In his rule variations table The Wizard says that double down rescue lowers the house edge by 0.10%. Unfortunately, nowhere on the site can one find explained the mechanism of this reduction!? Does it follow from surrendering after unlucky doubling, or from doubling hands one shouldn't double if DDR was not available?

Interestingly, when I thought of this question I remembered that none of the strategy calculators I have seen which included DDR showed ANY doubling of soft hands - probably because it was not allowed!?

I wonder if there is a source that calculates what hands should be doubled under DDR?

As far as I know the only hands you double down rescue are 16 or less when the dealer has a 8, 9, or 10 up, and 17 or less when the dealer has an ace up. There are no changes in basic strategy on what hands you would double down with..

Quote: miplet

As far as I know the only hands you double down rescue are 16 or less when the dealer has a 8, 9, or 10 up, and 17 or less when the dealer has an ace up. There are no changes in basic strategy on what hands you would double down with..

This simply is not true! I'm not sure if I can post links here, but I am looking at two basic strategy tables for playing blackjack at a certain casino, where some 'doubling' cells are marked 'DDR'! And, curiously, for some reason(?:) here you do not double any soft hand!?

Quote: Jess

This simply is not true! I'm not sure if I can post links here, but I am looking at two basic strategy tables for playing blackjack at a certain casino, where some 'doubling' cells are marked 'DDR'! And, curiously, here you do not double any soft hand!?

Yes, please post the link. Maybe I didn't make it clear, but you double down on all hands that you would double down even if you couldn't rescue. The only time you would rescue your hand is when your final total is 16 or less and the dealer has a 8, 9, or 10 up, and 17 or less when the dealer has an ace up.

I wonder what part of my post may be interpreted as a question when to rescue!? And yes, it is obvious that "you double down on all hands that you would double down even if you couldn't rescue"; my question is if you couldn't double down profitably some more hands!

We need the exact rules of the game. Are there doubling restrictions or not? There may be times to double a hard 8 or even a 7 but we need more information. Please post what you have.

Also, if you double down on a stiff and bust, can you take DDR then? If so, it may be worthwhile to double for example a 12 against a 6.