Since the shape is organic and not a pure cylinder every method I attempt when trying to make a UV map of a sleeve of a T-shirt I cannot get a square grid in the UV editor. This is the closest I got to having a grid. Ctrl+V just makes a mess. Besides editing every single point I have no idea how to achieve this. Pictured is half the sleeve mapped.
The suggestion of Follow active quads gives me a skewed diagonal irregular large on top smaller at the bottom grid.
New information, new problem:
It was suggested to use the The UVSquares addon in the possible duplicate entry. I followed the UV squares addon tutorial, I didn't have an entry for "3D view: Screencast keys" so I found it and install it from file and activated it. Done! But I do not have the "Mesh: UVSquares" entry to activate once I installed from file the uv_squares.py
What can I check to get it to work?