Yup it's called fish scaling. I did that when I repaired some bad spots on my frame.
3/16" works fine too for plating the frame. That's what I used.
It's also far easier to use with a smaller 115 volt welder since you can get better penetration than using 1/4" but if you have a larger welder it's not really a issue.
Maybe different parts of the world are different, I've always called it a "fishmouth", but same deal...I found my 110 welder was more than enough for my 1/4 inch plating as the frame is not that thick, I was able to just concentrate mostly on the plating, and the welder was plenty hot to melt through the frame.
