To inform you, there is no own testing track.....

4S is indeed getting a standard, I believe in the offroad it is already a rule. I rather would have seen a mounting for 2x 7.4v packs, those packs are easier to find and becomming cheaper every day. And I wonder if an adapter will be published to charge the 4 single cells as one battery, such a solution is already to find for 7.4v packs:



With 2 spare MRX4 cars and a brandnew Protech VXR8 car I do have some thoughts to convert one. It is just to difficult to choose the right engine and gearing, I know thats why some pioneers have burned up some motors....