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…

The dilemma is if you are playing luck-based games like what you mentioned, roulette, you are still relying on your luck. And you can even lost all your succeeding bets and not win at all. What are the odds, right? So I won't be very confident that such strategy may give me winnings. Always consider the side that you can lose all your bankroll in one sitting.
You have been using this for over ten years now and you have had more profits than losses. It's hard to believe that such a betting system can work for such a long period of time. Placing multiple bets at the same time is very risky because there's a high chance of losing everything. You also claim to be a pro at this strategy. If this is really true then you must become really successful from gambling now. If you can show us some winnings for us to be convinced that you are as good as you are then this would be valid.
Hard to believe such claim. We can't validate its veracity. If that strategy worked for him, then, great! But for others, don't just believe what you read. Most of the time, those are false claims. This is gambling, and no single strategy can work in this game to accomplish a series of winnings without losing anything.