Sigh..... here we go again.
This is the last thing I'm gonna say about pipe vs. tube in this thread:
Do some research and you'll find that pipe is made from the exact same materials and by the same process as HREW tubing. NO I didn't say DOM tubing, but that's overkill most of the time anyways.
Pipe and tube both have their uses. Pipe can be a safe, cost-effective alternative to tubing in non-structural applications such as bumbers, sliders, etc...
Remember that we are replacing a bumper made from sheet metal. I garuntee you that a properly built pipe bumper is going to be 10s if not 100s of times stronger than the stock bumper. And sliders.... ha! there weren't any to begin with.
So I probably woudn't use pipe for a cage or frame, but it is perfectly safe and suitable for bumpers, sliders, roof-racks, etc...