> My thinking is that sheet goods are made 4 feet wide, and 3 times 16
> is 48. Thus the sheet goods do not require trimming to fit framing on
> 16" centers.

That's why sheet goods are made 48" wide -- so they don't need trimming
or fitting over standard 16" on center framing. The 16" was standard 
long
before sheet goods, back when walls were covered with lath and plaster.

Mike in Sacto