Re: no problema
Your right in saying that different professionals show different BS charts. You're wrong, however, in assuming that means their opinions differ when it comes to "the right play". At any one time, there's only ONE correct BS play. Stanford Wong prescribes a "generic BS" because he moves between single and multi-deck games and this form of BS lets him play any one of these. Some other authors prescribe BS for what they play. The BS of a single deck, double deck, 4-deck, 6-deck, etc. are all different, just like rule variations can cause the BS to differ. Index numbers also change with each of these variables. Performance numbers can also change. I believe the Mayor posted something on how KO Blackjack manipulated the conditions to suit their system better.
Regarding Stanford Wong and Doubling 7's, p. 46 of PBA (S17 Indices) show double 7 against 5 and 6 at +9, p. 48 of PBA (H17 Indices) show double 7 against 5 and 6 also at +9. p. 41 (Double Down S17 Table) shows the same thing, double 7 agains 5 and 6 at +9. To be fair, Stanford posted, it looks like, over 100 index numbers. I would only learn maybe the top 50 and thus far, it seems that doubling 7's wouldn't be on that list.
Mayor, are you sure that double down on a 7 is meant for the SD game? "One that comes to mind, e.g., is doubling 7 vs. 5 (single deck)." I thought PBJ was based on multi-deck games, and with the exception of Vegas SD games, most places don't allow doubling on 7's.
I think you're both right. Stanford DID publish doubling on 7, but many authors left it out because there's a lot more profitable index numbers to remember first.