I'd like to add something about your dozens/columns matrix.


If we would use 3 x 3 matrix in order to cross reference rows and columns it would look like this:


1,2,3 horizontal rows as reference to dozens.
A,B,C vertical columns as reference for columns.


Let's say that the last spin was number 24, it belongs on 2nd dozen and C column, write on the top left box 2 C.
Since there are more ways to have 2 different dozens and columns on 3 spins we should bet for the other 2 dozens and columns simultaneously.
So the bet would be dozens 1,3 and columns A,B, total 4 units.
For the example's sake the next result is 21, which belongs to the same dozen and column, we lose 4 units and you write on top middle box of the matrix 2 C again.


There 9 boxes for equivalent total of results, out of 9 spins we are betting max 8 times, from those 8 we are expecting 1 simultaneous win for dozen and column, the payout is x2 net.
Divide -4 draw-down by 2 net payout = 2 but since we want to win rather than break even we would bet 3 units by 2 dozens and 2 columns = 12 units bet.

The third result loses for dozens as the 2nd repeats, but the column changes from C to A as the 13 comes.
So we lose -3 on top of current balance of -4 and now is -7, divide it by 2 and we find 3.5 which means 4 units per dozen and column for a total of 16 units (4 x 4).
Write 2 A on the top right grid of the matrix, now we bet dozens 1,3 and columns B, C.
2C 2C 2A
1A 1B 1C
3C 3A 2B

Let's say we lose 5 more bets, -7 + -4 = -11/2 = 6, -11 + -6 = -17/2= 9, -17 + -9 = -26/2= (13) 14, -26 + -14 = -40/2= (20) 21, -40 + -21 = -61/2 = 31 units x 4 (2 dozens + 2 columns) = 124 units max bet + 61 draw-down = 185 units BR.
This final 8th bet/9th spin concludes the series with a profit of 1 unit.

Thanks Alrelax,
Thanks BlueAngel, for your interesting matrix,

Coincidence does happen but to extended limit.

Another way to bet 2 dozens + 2 columns simultaneously is to look for repeat of dozen and column in last 2 spins, in such case bet the other 2 dozens and columns.
Also when there are 2 different dozens and 2 different columns on the last 2 spins then bet all those for the 3rd spin to be double repeat.


We are betting against: 111, 222, 333 and 123, 132, 231, 213, 312, 321, for dozens and columns simultaneously.
Those are 9 permutations, we have 18 on our side, double more!
We double win from column and dozen by 16 numbers, it's very hard for 16 numbers losing 8 bets consecutively.
From the other side there are 5 numbers which make us lose all bets, those 5 numbers could come for maximum 7 times in a row, since the last 2 results are the trigger we could have 5 loses ahead of us in some extremely rare situations.