Before last year I would have said positive G's.
Last year I was able to ride:
Shivering Timbers @ MichAdv
Excalibur @ FunTown in Saco, ME
BoulderDash @ Lake Compounce in Bristol, CT
Superman: Ride of Steel @ SFDL, SFAmer and SFNE.
I'm now a proponent of negative G's and even leaning more to wood than steel, and out-and-backs over inversions.
If you haven't been on Shivering Timbers or a similar CCI woodie, do yourself a favor and get to Michigan's Adventure on Saturday and Sunday, June 9th and 10th. (3 hours of ERT on Sat. evening)
You might look at AIRTIME from an out of seat perspective.