If you are familiar with the 'Keefer' system (betting against each other), you know it won't work because of the martingale risk with a losing streak . So I was thinking: what if you make Dozen 1 and 2 one part, and Dozen 2 and 3 another part, and treat them as even bets?(64% over 49%)

For the progression, if one side loses, you only add 1 unit. Here is how to begin: you start to bet, for example, on Dozens 1 and 2. If you win, you repeat the bet. At one point, if it loses, then you add 1 unit on Dozen 1 & 2, and 1 unit on Dozen 2 & 3. So, Dozen 1 & 2 will have 2 units and Dozen 3 will have 1 unit. Thismean Dozen 2 have a total of 3 units. ( you can cover 0 )

You keep adding 1 on the losing side, and the other side stays at 1 and reset after positive win. If you are lucky, Dozen 2 will win at some point ( jackpot). I only tested it on a tracker tool, but it needs a lot of spins and some tweaking and maby set cap to prevent a long streak. let me know what you think?