you need to take into consideration areodynamics at the speeds you are reaching, they will drastically improve stability and prevent fly away... and dont forget about diffusers for any air that is under the car, give it a way to escape so that your car doesnt end up floating on a pocket of air... also when doing these high speed tests make sure your track is secure to the floor, that way the energy being put out from the car into the track isnt being wasted, it will result in even faster car
On the side wheels using the rubber covered ones, if you could angle them down slightly (as seen from the side and down angle towards the front, might help steer the force downward sort of like a mechanical downforce
