Ace top/side curtain ferrule question

[aex125]

When I removed the top/side curtain ferrules on my Ace I ended up destroying most of them due to the fact they were rusted in place. I am now in the process of making some new ones and noticed that the inner diameter is not constant on the 2 that I was able to salvage. For most of the length of the ferrule it has an ID of 25/64", but for the top 1/2" it is slightly wider. I do not have any side curtains or top bows as of yet (let me know if anyone has any spares that they want to part with) so I cannot check to see if the wider diameter at the top serves any purpose. Can someone check (or does anyone know) if the top or side curtain has a shoulder that needs the extra width to fit properly? I would like to make sure I have everything correct before sending the parts out for chroming. I believe these are same as was used on the Cobras, so info from a Cobra owner would work.
   Thanks,
   Jay

[Gus Meyjes]

Why go through the trouble of making the ferrules. They are widely available, both in alloy or in chromed steel,  particularly in the US from various Cobra parts vendors.
   
   Gus

[aex125]

A couple of reasons, first,when looking at the pictures available for the ones identified as OEM versions, they are very different from the ones I have. They show a beveled top where the ones that came off my car are flat on the top and have a small relief cut on the edge. I suppose the pics may be in error, but I have been burned by a couple of the US based suppliers with supposed OEM style parts that are not close to the originals. The second reason is I recently bought a lathe for a couple of other projects and decided I might as well use this as an excuse to get more practice in. If I had confidence the available parts would have close to correct, I would have gone that route, but now the new parts are machined except for the portion I have the question about.
   Jay