Disable I2C/TWI on Orange Pi Zero with legacy kernel

I'm working in a project that needs to use 12 GPIO pins (plus serial!) on the Orange Pi Zero. To achieve that, I need to disable at least one of the I2C interfaces in the 26-pin header. Following the instructions on https://linux-sunxi.org/I2Cdev, I have decompiled, edited and recompiled /boot/config.bin, but I still can't access any of the pins used by the I2C ports.

Specifically, what I have done is to edit the decompiled script.bin.fex file, and in sections named [twi0] and [twi1], changed twi_used=1 to twi_used=0.

After that, running a simple program that sets the pins to input and reads its status allways returns 1, even if the pin is connected to ground or there isn't anything connected to the pin. Trying to activate the pulldown in the pin doesn't help, either.

Is there anything I'm missing? What else can I do to diagnose/solve the problem?