Driveshaft was underspeced evidently. There are critical specifications for driveshafts for specified HP/torque ratings. Beefing the floorpan was a great idea, but specing the correct driveshaft is needed too. Perhaps he's exceeded the driveshafts available commercially ?
I'm sure he was smart enough not to be using a stock GM Camaro D/S?
Glad he survived . He's very lucky.