Now I am attempting this for the first time. It was forced upon me as I bought pickling onions thinking they were shallots (my crop of onions was not that good this year and got used up quickly in casseroles etc.).
I am going with an improvised method and recipe as there are only a few onions to use up. I will post updates on the progress of my pickling onions attempt. If the pickled onions turn out great I will post the recipe. I am adding hot things like a dried chilli pepper to the pickling vinegar as the family enjoy foods with a 'hot kcik'. The chilli in the pickling mix is the wild card not sure if it will work well or prove overpowering .
Here is a video that I am using to prompt my memory on just how pickling onions should be done the traditional way.
Using allotment grown onions to make pickled onions.