Do you mean this?

https://www.columbus1919.com/wp-cont...es-Catalog.pdf

It does seem to just go all black for me after a few pages. Maybe just find an older one.

When you say shape do you mean the ovalness or the bends? Basically the cross-section at the end is mostly about 30mm/18mm oval or 22mm round. I think round/oval/round is better, although tricky to weld since it's quite tight between them. Doable though. Idk about fillet brazing.