It has to be a 5-card 21 though(forgot to mention that).. So it only helps by .24%. The "Wizard of odds" list this rule. So according to your analysis, were looking at .19% + .24% -.91%= .48% House Advantage.
Im just wondering if it would still be beatable since BJ only pays EVEN money...
Not sure if this game is any good or not because blackjack pays EVEN money only, but it has a list of bonus rules, which may or may not give a decent Win-Rate. The additional rules are
4 standard decks:
Full Early Surrender(against Ace or Ten)
5 cards or more automatically pays 2 to 1...