While I understand why most don't trust wikipedia, it's not like 3.7 G's would be unrealistic. Maybe this will help:
Q: How does the lie-down dynamic change the safety tests performed? Does it affect the maximum allowable G-forces on the body? Also, what is the standard Safety Factor for a roller coaster like Manta? This one's a bit of a nerdy engineer question, but I'm curious.
A: Answered by Mike Denninger Dir of Corp Rides and Maintenance
While the prone ("flying") riding position of Manta puts riders in an orientation that differs from many other coasters, it does not alter the orientation of the axes by which biodynamic accelerations are measured.
Great second question! The "flying" riding position of Manta reveals that the accelerations traditionally experienced by a rider on a sit down coaster like Kraken, are experienced quite differently when "flying" on Manta. For example, at the bottom of Kraken's large initial loop (after the first drop) a vertical acceleration in the rider's "eyes-down" or "z" direction is experienced. This makes the rider "feel" like they are "heavy". Now comparing to Manta, at the bottom of the dive loop (after the initial drop), a similar vertical acceleration as on Kraken is experienced, but this time the rider is "flying" on their back at the bottom of the loop, and the acceleration is experienced in the "eyes-back" or "x" direction by the rider. So instead of "feeling" heavy, the rider experiences a unique feeling of being "pulled" into the back of their seat. You might relate this feeling to that of accelerating in your automobile on the highway, and being pushed into the back of your seat. As you can see, this rotational difference of the coordinate system results in the need to review biodynamic measurements differently for a "flying" coaster like Manta than for another coaster like Kraken.
With regard to maximum allowable G-forces, ASTM International has published a Standard that details the specifics of acceleration limits for all types of rides and we always adhere to all standards.
Bolliger and Mabillard Consulting Engineers Inc., the same team of engineers and designers that worked on Montu, SheiKra, Griffon, Apollo's Chariot and other world class coasters in our parks, performed the engineering, design, and fabrication work for Manta. While Manta is a uniquely SeaWorld attraction, it is first a very safely-designed attraction. In addition to the exceptional engineering, calculations, and design work required to fabricate and construct Manta, sufficient safety factors were applied in all respects to the many systems operating on this great ride.
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http://www.themeparkinsider.com/flume/200905/1194/