A magnificent machine- truly a thoroughbred. The story of the structural problems tearing wings apart is an interesting story and well described in "The Electra Story". Well worth reading if you can obtain a copy.
Basically the gyroscopic effect exerted by the 13'6" prop in turbulence could not be dampened by the engine mounts and exerted a twisting force on the wing that increased until the wing snapped. Hence the initial fix by reducing airspeed to around 400 mph max.
After stiffening the eng mounts the Lockheed test pilots flew the aircraft at increasing speeds and turbulence until finally flying at vne in severe turbulence over the Sierra Nevadas with the prop attach bolts slackened off.
End of problem. I dips me lid to those guys!
Emeritus