I do not know the definite answer, but I'll have a crack at it..Having an extra row would cause a lot of extra weight, meaning that more energy would be lost during the ride. For example, taking into account Newton's 2nd Law (Force=Mass x Acceleration - F=Ma), and rearrange it, acceleration = Force/Mass. The (g-)force of the ride would stay the same no matter what, but if you increase the Mass with an extra row, then the acceleration would decrease. This means, there'd be less speed and it would be harder for the train to get round the track - and probably cause it not to complete the circuit more often then not. Therefore, if they wanted an extra row, the circuit would have to require a larger lift hill, shorter circuit, smaller elements; etc. so the train could complete. As this would probably affect the experience of the ride, they've probably stuck to 7 rows, as opposed to 8. Things like this are usually taken into account when designing rides, of course.Again, I do not know the answer, and I've used probably there upteen times. However, it's just my understanding of Physics that I've got and using a bit of guess work, this is what I've always believed to be an answer to such questions for any coaster. Of course, if I'm wrong, someone will say and give the right answer. Hope this has helped a bit though James.