The bike has main bearing housings with small diameters within the manufacturing tolerance range. The crank is near to the maximum allowed diameter. The thinnest white coded shells are used. It is likely the oversize shell is a green or blue shell for a larger diameter crankcase bore. Some idiot put a white paint code mark on it and put it in a bag labeled for a white coded bearing.
The big shell caused part of the main bearing housing to break off at the edge when the cases were assembled. This is what I did and my mistake is in bold type.
White shells worked in this bike in the past so I ordered a new set, put them in, laid the crank over them, laid some plastigage on the journals, placed the other case on top, and tightened all of the bolts. The goal was to split the cases, look at the plastigage, and look at the compression marks on the back sides of all shells. I ASSUMED all shells were correctly sized white shells and any shell thickness adjustments would be made after looking at the plastigage.
That step when the shell thicknesses and projections are measured should be done first and before the cases are tightened down for the plastigage measurements.