I am running Robotronic 4600 35C cells and they are in with no problems or mods.
I have to run a minimum of 30g just to make the car legal with those cells in and that is in teh form of lead plates stacked in the spine of the chassis. I have lead plates that fit under the LiPos (now you have to modify the car with taller battery posts) as a tuning aid and these take the weight back up to where the car was on NiMh cells.
I will be honest and so far I have not run the car without the lead outside but indoors on carpet the car is better in light weight mode, how it will react to the bumps without the extra weight I am not sure ... be in a better position to answer after the weekend as we are trialling some stuff @ Kidderminster.
Not sure how long you have had the FS but great to see you have joined those that know and drive Kyosho
