This is 12 numbers bet, FLATBET.
Procedure: Wait for a SINGLE (after a switch of colors) Now bet that this Single will become a DOUBLE: RR, or BB.
Bet all numbers of the same color in the two unhit dozens: (12 numbers bet).
After 3 losses in a row STOP. (and wait for a virtual win before betting again) By "virtual win" i mean RR or BB, (no matter if hit in the same doz or not!)
First tests was played with 5u bets.
3/3 Games won
It takes time to grow +100 by flat bets, but you are almost sure to be on safe ground here.
Thanks Ig!