[niles]

Tommy is right on.
Tubes are stronger; a little more on this:
if your permently "setting - twisting" a shaft, your already on the direct course for failure! That fact says that you are exceeding the yield strength of the material in torsion. That being said you are now on the way to "definite" failure after X number of cycles at that stess level. NO proper design ever operates at or near the yield strength of the material in question.
Would you think it OK after a rough airplane flight to have the wings "permently" bent up a tad?

gn