To get a reverse shuttle launch, you would need a head restraint that is like those haloes worn by people with broken necks. Too time consuming, and too many possible lawsuits waiting in the wings...
I would like to see a nice long layout, perhaps twice the size of Dodonpa (Peabody, you lucky guy, you) with a second, in transit, launch for a series of hills and perhaps a tunnel. I would love to see a vertical drop into a very deep tunnel, ala Oblivion! Scary...:)
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;)Rollercoasters are like parrots...if you take care of them, they should outlive you;)