Looking good there mate.

One thing I could/should of let you know was. Steel/Ali will stretch in lenght by the thickness of the sheet being pressed. E.G A 2mm sheet will gain 2mm in each direction of a bend on the opposite side/outside of the bend.

If you would like a C channel shape that is 100mm x 100mm x 100mm measuring the outside.
You will need to cut and bend like this 98mm x 96mm x 98mm.

You will have probably worked this out by now.
Sorry for the late info.

Keep up the good work.