I see your point. I actually do run outdoors and have the usual wear on the left rear of the chassis. It is not a problem do to the hold down spots. They are pretty far in. The chassis would have to be worn to the point of needing to be replaced for this to be a problem. Also, I only put the ledge in the very front and back so you can see that the area under the chassis in the middle lays perfectly flat. The minate you see this thing and hold it in your hand, bolt the car up to it, you will see how far off what we thought was straight is. I used it today on Jarrod Scott and Steve McNichols' car. They loved it.