I'm guessing you mean a helix that turns right but is banked left or vice-versa. I don't see the point in that. I mean, think about it. Now, I'm no RideMan (;)), and I've never even taken physics for that matter, but I'll just try to explain why I think this won't happen.
If the track is turning right, but the bank is left, wouldn't that push the rider's body into the restraints? I would think that would cause some pretty interesting pain.
It's almost like the Superman: The Escape question. (I think that was another thread...) Somebody thought it would be a good idea for S:TE's trains to be turned around so you would go up the spike backwards. The problem there is, upon launch, you would be pushed into the restraint instead of the back of the seat.
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Matt Lynch
Co-Webmaster, Kennywood Boulevard
http://kennywood.coasterbuzz.com