I haven't been a player who has often gotten a peek at the hole card. But I'm curious about it for those who routinely are able to do this. What do you do on the plays where it just looks either too stupid or too suspicious to make the correct play. For example: you have a 19 and you know because you know the hole card that the dealer has a 20. Or you have a 16 and you know the dealer has soft 17 with an Ace under and he has a 6 up. Or your 18 against his 19, or your hard 17 against his 18. How do you handle it? How about doubling when you have 8 when the dealer has a 9 up and you know he has a 7 under?
Regularly catching a hole card at Blackjack gives you a significant advantage in the game, however, you will have to institute, 'Cover play,' in order to extend the game and/or not get caught doing it. Cover Play is any play that is less than the Optimal decision in order to conceal what it is you are doing and the fact that you have an advantage overall.
I will let somebody who regularly hole cards confirm this, but I would suggest that most of the plays that you have suggested would be entirely too obvious to do with any regularity, or in combination with one another, and it wouldn't take long for you to be found out. Hitting the sixteen against the soft 17 might be the only exception, but I'll definitely let someone with more knowledge about the matter than I have speak to that specific play.
The nice thing about hole carding is that you will often find yourself not playing in accordance to what would otherwise be Basic Strategy, so to a certain extent, you can just look like a really bad and erratic player. Many BJ players are both bad and erratic, so nothing unusual there. However, if you routinely make plays that are just flat-out ridiculous, and some that you mentioned I think no sane person (without hole card info) would ever do, and your chip stack keeps piling up...surveillance is going to get interested in you in a hurry.
I also suspect that it might be bye-bye for you if that happens. Again, almost no personal experience, but I bet they are more lenient towards card counters than hole-carders.
For starters, no, I would not hit 19 against a known dealer 20... nor an 18 against a known dealer 19 =). Maybe 17 in a negative count (if you're still counting out of habit) but I would also make sure it's going to fly (know what the pit already thinks of me). Basically no.. I wouldn't recommend you hit 17 either. Just eat those losses... You'll more than make up for it on the other plays.
Also, flat bet near your top bet, but something that won't draw crazy attention. Don't think "omg I can make $10k from this game tonight!" ...instead try to think "omg I can make $100,000 from this game over the next year or more!" Don't burn good games down please =).
There's several others that should definitely be avoided in general, especially if it's valuable and you don't have a lot of known competition. 17+ is the never ever though.
The nice thing about hole carding is that you will often find yourself not playing in accordance to what would otherwise be Basic Strategy, so to a certain extent, you can just look like a really bad and erratic player. Many BJ players are both bad and erratic, so nothing unusual there.
Again, almost no personal experience, but I bet they are more lenient towards card counter than hole carders.
First paragraph, the bad and good thing that makes that not entirely accurate is that 90% of supervisors are just completely brain dead, and 90% of casinos are sweaty shitholes that sweat any 3k swing. At some point they don't care if they really have any clue they just won't take it. That's how ploppies get backed off too...
Last paragraph mostly true but depends actually more about stakes being played and the casino in question than if HC or counting in my observation/experience. If they don't have any clue what's going but just not comfortable on you maybe more likely to just get a normal backoff than a counter who they know what's going on.
How about doubling when you have 8 when the dealer has a 9 up and you know he has a 7 under?
Rule of thumb for me not unless you're at least matching upcard. (8 vs 7 ok to double, 8 vs 9 hit).