I had to cut the awning tube on my old motorhome.......I was replacing the arms and related hardware and I had to shorten the tube by 1" on both ends.......
I unrolled the awning and supported the tube with a 6' ladder....I removed the hardware on one side at a time.......I then used a large hose clamp to mark where I wanted to cut the tube.....then with a jig saw I cut up against the hose clamp.....the thin tube cut very fast.....
I then installed the new arms one at a time and it was done.....not a bad job at all!