You should know that the function of the average pure income for the fixed percent depends on the coefficient, and it depends in that way, how the function of the sum of the stake depends on the coefficient and its dependence is reverse.
Please read the beginning of the fixed income betting strategy
It seems that the last function crosses the line S1*C in the point (S2/S1) +1, besides, because of the function f2 (k), which is decreasing all the time, the pure average income to this point, using the strategy of the fixed percent is bigger, than using the strategy of the fixed sum of the stake, and after – it’s less, for the same K.
You can make the conclusion then: if the quality of your guesses is bad (it means that C<0, what is equal to the K*P(K)<0, and your guesses have minus mathematical result) both strategies won’t bring you any income and you don’t have to use them not to lose more. But if the quality of your guesses is good, you can. Manipulating these strategies, increase your profit.