Replacing floor sections

I was just looking at the cars under construction section and was thinking back through the many replacement floors I have done over the years . As the dies have worn over the years it seems to me that the channelling in the sections [the floor swaging ] has become shallow and when these sections are hammered or shaped to match the cross section of the existing floor, the floor section [patch piece] can then shrink in area as you tap down on each depression. It was a bit of a guessing game in the past but now with plasma cutters more common place and these very thin cutting discs the job is a lot easier but it is still important to leave the final trimming until the floor is shaped and also very important to spot weld the floor to the subframe before welding the perimeter as the heating and cooling of the steel [cause shrinking] can lift the section away from the subframe . I'm not sure if this floor section problem is a local issue but these days , unless someone brings their own floors for a job I usually make my own .Haydn