I addressed these clocks earlier in the thread. Yes, the three clocks start simultaneously in the ground frame. Since they're in the same position in the direction of the tank's travel, they also start simultaneously in the tank frame and the upper tread frame. Yes, that's correct. They would be incorrect, since they are calculating speed with tank-frame lengths and ground-frame clocks. A smarter normal person would place two clocks a known distance aparton the ground (say 20 feet), synchronize those clocks using any method you like, then find the time (23.5ns) it takes the front of the tank to get from one clock to the next. Then, they can correctly calculate the ground frame speed of the tank: 0.866c. Using your setup, the ground observer can determine neither the speed of the tank nor its length. They can assume that the length of the tank is the same as it was when at rest, but why would they do that when with a little more preparation they can measure the speed directly and thus deduce the length?