i now cut away 4mm from the right hand (drive) side and cut away a bit of the mounting flange. it's a perfect flush fit now. and as far as i can see no collision of any parts that shouldn't touch. i'm really happy how it turned out, and i think it was the right way to do it.
i also made a programming connector and will see how programming can improve the kit even more.
unfortunately the on/off switch on the battery (bottle mount rectangle one) doesn't work anymore after 5x on/offs. pretty poor quality. i will have to replace it as the battery can't be turned off now (the kit of course can be turned on/off, but the blue battery led is always lit)