Very interesting question!
I think you are right. I would have used the same formulas but this doesn't mean that it is right
I'm curious to know what the other members think.
What is different between a pipe and a "classic beam" is the internal stress.
As you see, the pipe is subject at the following stress:
- bending: the moment of inertia of a pipe is different from a beam
- transverse shear: the shear factor for a pipe is different from a beam.