I tested this strategy on a live spins from a live online casino. In its original form, it often loses.

Then I change it a bit.

Bet 3 numbers within each dozen SAME (hit) DS and same color. Example: last hit number in doz 1 was black 11 - now you bet all black numbers in DS 7/12. The results were better, but still a lot of failures.

Then I still change strategy a bit.

The numbers for the bet select all of one color, which more. DS remains the same.

Example. Last hit numbers in each doz was 4,19,36. Now we bet only on RED numbers (because 2 red and 1 black): 1,3,5,19,21,23,32,34,36.

Placing bets on the usual negative progression for 9 numbers (see the attachment). Max 9 steps (after that need BR is too big).

With this betting system I was able to get the best results. In the attachment numbers is the amount of winning units. When lose in brackets I wrote the number of the winning spin.

However, this betting system still often loses and need big BR.