Extending and Modernizing CSS Orange MU's

In the 1940's and 1950's, some of the orange P-S cars were lengthened. It looks like the added sections were riveted, just like the original 1926 and 1930 parts of the car. Can anybody confirm this? And or shed some light on why the cars weren't welded? By the 1940's most steel fabrication was welded.

no exact answer but any repairs you don't have to cut thru the body, just release the rivets. Perhaps in a collision the rivets will fracture and not buckle the body.
I'll have to check my books later on it.