When I have 19 and dealer has a 10, my understanding is that it is negative EV before dealer checks his hole card, but if he does not have BJ, then I have an advantage.
However, if the count is high, does the advantage switch to the dealer? If so, at what count?
For example, if I have next card info, I have 7,4 and know that next card is an 8, and dealer has 10 but no BJ, should I not double at a TC of +10 HiLo (RC of 21 with 2 decks remaining)?