I've been thinking of a possible partnership or a "single player with a virtual team" concept.
It seems that two players functioning as a team and betting progressively after either winning or losing, could both win if they use the same system but bet on opposing EC's. An example might be...within 6 spins player A loses 2 bets on red, while B has won 4 of them...a net of +2 for the "team" or in 4 spins one player loses 2 red bets while the other was playing black.. net loss =0. This concept has an appealing virtue of smoothing out peaks and valleys in each of the partners' results.
A roulette team with two opposing bets on the table would pay a high price if a zero turned up. If their wagers had been $20 and $30, their loss would be $50....contrasted with just $10 if they had bet only the net difference.
The solution could be that one partner does the betting for both. The other partner with (possibly a scratch pad) keeps track of the figures between the two opposing positions and calculates the net difference between the next two bets that their system calls for. He/she then tells their partner the single bet that reflects the difference.
Actually a single player could do this, by figuring the net differences and betting them accordingly.
A crude way of showing this might be - at a particular time red may be dominating black by a ratio of say 5 to 2....
Rather than loading up on red or black (whatever the method), the bettor places the difference (5-2) = $3 on whichever color. This could soften those pesky and damaging bankroll whipsaws.