I think you cant actually! But im not sure to be honest. I know there is a parameter on settings.ini where you can edit a bit the behavior of KERS but i think not how long it takes. But have a look and try to find it. Im not sure if its in settings.ini or another .ini file on mydocs/NSGP/
You can edit how fast KERS kicks in and how much draft you have.
If you find how to do it, write it here so others can know how to do it.