Years ago my original driveshaft suffered catastrophic failure on the dragstrip and the only thing inside the tube when we retrieved it was a cardboard cylinder that appeared to have approximately the same OD as the ID of the shaft tube. Couldn't tell how long it had been because it had unraveled somewhat but it may have been close to the same length as the shaft. I believe the failure was on the part of the front yoke or u-joint, not the tube itself.