Advice wanted: patching trunk flr/inner whl house

[Schonyenko2]

You'll be ok joining a partial onto the existing inner depending on the ability of the person welding. Butt welding is good if you get a good match. Trying to fill a gap goes back to the welders ability. A small overlap flanged in will work too, and is easier. Don't forget the weldable primer.
It's all in what you're comfortable with. As long as you're happy with the fix when your done.