I've looking for the correct play for doubling down 11 vs 10 with European rules (no hole card) but I've seen very different results (from true count 3 to 12) depending on the book? Could anyone help me on this?
Basic Strategy calls for not doubling down 11 vs 10 with European No Hole Card rules, as you lose both bets if you lose, as opposed to more standard rules when you only lose one bet. I'll leave it up to the experts re: what do do at different counts. I play a wierd hybred game where you lose both bets vs a 10 and only one bet vs an A. Basic then calls for not doubling down 11 vs 10 and doubling 11 vs A. Splitting 8's follows the same logic in the game I play, where I split 8's vs A and do not vs 10. I hope this was at least some help.
The EV-maximising index for 11v10 if you lose all to a natural is around 3 or 4. The risk averse index for this play is much higher (depends on spread, rules and pen but generally >6). Best thing is probably to stick to basic strategy for this play - it's not much of a money-maker with ENHC.