Ive had to do this more than once, raise or lower part of the string to increase or decrease bass. Usually its been a case of too much bass, kinda just an everywhere woofiness. I find just upping the resistor value a little can make things clearer.
I did a kinda AC15 clone recently. Thought i would try the Zwreck string and cap values. Using the spec R's it was overly bright, or light really. I dropped a few K off the last dropper and it fattened thngs up perfectly.
I know theres basic laws at work but im nt smart enough to know them
I do know lower the dropper a little, thicker tone, raise it a little thinner tone.
Of course big changes also alter operating points, and can make cleaner of gainier amps too.
With the AC15 thing, i dont believe i lost or got any mre gain or cleans, just fatter all round.