Square, Round, Triangle the concern should be the safety of the tank. I believe a concern with the original design was that the tank was attached to the bumper underneath the tank. An obvious concern if a hard rear, or side, impact happens in such a confined space. If that was corrected then all is well, old tube size aside. The promoter made his decision and you live by it. Put the effort into figuring a way to beat them. I believe a victory using his equipment and your obviously superior intellect would quell many a doubter. I say take him up on his offer and put all your resources into the one car and lets see what ya got Don.