To do: needs angle iron to spread load on axle.
Load bearing flat area for jack head and non load bearing locating lip.
One thing that could theoretically go wrong is if the jack is lowered quickly without engaging the prop.
Could maybe punch a hole in the body.
Main advantage is speed of use compared to jack stands.
I service our two diesel Mondeos as a hobby, being elderly it also serves as exercise.
With four jacks I can raise the whole car and rotate tyres cheaper than the gym.
I have also made a wheel dolly which I use to lift wheels of the studs. Will post a pic.