Adjustable regeneration and regenerative braking

The amount of regeneration can be adjusted by supplying a voltage between 0 – 5V to the PEU. ECE decided to fix the voltage, at a safe level, with two resitors (2K2 and 3K3). I want to be able to adjust the regen,. E.g. in rainy conditions reduce the regen and in summer when using the Yokohama’s A048 increase the regen. I did some testing and it is unbelievable how much braking force is available when set to full regeneration.