Multiplying the bet amount by 7 times isn't bad at all. I thought about applying this strategy to other games, like roulette, betting on black or red, even and odd, 1 to 18–19 to 36, for example. Splitting it into 3 larger bets, approximately 33%, on each, instead of choosing one number, which pays more, but is also the most difficult.

It may not be feasible, but OP's strategy gave me some ideas…