My apologies for the delay in responding.
I have concluded that my problem with My Maps failure is that Google Maps seems to expect the input data file to be the length that is needed to hold the data. I created the file using processing methods which filled the unused portions with nulls. As soon as I changed my software to use only the file space required, MyMaps worked as expected.
I consider this post as complete and, again, my thanks for your efforts on my behalf,
Fred Stout
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