Funny you should ask, I just shortened one today for someone.
BUT.... I'm going to be right up front and say that I used to be an automotive mechanic and have all my own tools, and now that I'm retired, built up my own shop in my garage.
This is ONE WAY to do this, and there are many other ways to accomplish the same thing.
You will need some basic tools, good saw, a welder (or access to one), and grinder.
I took a magnetic angle block for welding and used it to make four straight lines to keep the the angles right. Use a marker or sharpie for the top one at both ends of the scribe.
This will be explained later.
Then I used a punch on one of the lines to mark OUTSIDE the cut area to measure the total cut length.
Then I cut about 7/8" out of the lower portion of the tube. Try to find some pipe or rod the same as the inside diameter to splice it together. I have a metal lathe, so I turned down a piece of solid rod I had laying around.
After cutting the 7/8" out, I used a bench grinder to straighten the edges out, then wire wheeled them. I then drilled three holes in each piece near the edge. Cleaned the inside of the tubes with a sandpaper drum on a pneumatic grinder. That sleeve I made was pretty close to press fit, and should fit into place by hand.
I also drilled out the rod to lighten it up a bit.
Placed the sleeve in place into the lower portion, and welded it into place with rosette welds.
Now here is where the four lines around the shaft you made come into play.
Slide the pieces together and line up your scribe lines being careful to get the color marks lined up.
This will make the angle of the foot pad pretty close to where it was.
Weld up the other three holes, finish off with some light grinding or sanding, and your ready for some paint.
After everything was done, it wound up to be shortened by 15/16".
Hope this helps.