You're going to have better luck if you pare down the categories. While a standard 5x5 League; (AVG, R, HR, RBI, SB - ERA, WHIP, W, K, SV) ...is the "industry standard", you can get away with adding "Bonus Categories" amongst your 6x6 or 7x7 League scoring categories.
I run an 8x8 League because I've known these guys since Junior High School. We've pared from a 10x10 League and it focuses our discipline. I've cried for 5x5, but our League remains friendly. We need "outside categories" to make bonuses strong and weak teams "eligible". I accept it but 5x5 is STILL the "industry standard".
15x15 is ridiculous. While I understand the inclusion, I miss the skill. You might as well throw darts at a board with your ass as far as I'm concerned.
While an idiot has a chance, another well-conceived manager has to compete against idiots.