Sorry, that's not a realistic value by any stretch of imagination, and realism's what I'm all about.
Su-27s and 33s have an imposed 26 degree AoA alpha limit, that can be overidden during emergencies. The Cobra maneuver is a "controlled" departure (talk about an oxymoron!). What actually prevents the aircraft from departing into a spin, is aerodynamic drag from the horizontal stabs when they are returned to zero deflection during the maneuver forcing the nose back down. I've been able to emulate this drag, in a creative manner, without compromising the model's flight characteristics in an arcadish manner.
The model performs the Cobra cleanly between 260-300 knots. Performing the maneuver at 300 KIAS, yields an 8.93 peak G-load, and scrubs off 155 knots of airspeed in less than 3 seconds, which still leaves you with just enough airspeed to maintain level flight at the end of the maneuver (that is, as long as one doesn't cut the throttle prior to the maneuver).