I am now getting some positive results to report, but mostly due to my own misunderstanding / mistake. Your first inclination was correct about setting one of the CRC modes. My mistake was that when copied the beta library you indicated to the libraries directory, I had renamed the original SdFat folder as "SdFatORIGINAL" before moving the beta copy to the libraries directory. While observing the verbose output of the compiler, I noticed that, even though I had been choosing examples from the SdFat library, it was compiling from the SdFatORIGINAL directory. After I completely removed the SdFatORIGINAL directory and re-started the IDE, it started compiling from the right place.
So, the success is mixed. The ReadWriteSdFat sketch is able to read and write to the card with the CRC check turned on. The Bench sketch runs without error, however, never ends, even after 5 minutes. Once I remove the card from the project and install it into my computer, I see the BENCH.DAT, but no data is in the file.
Given this, I'm going to dig into how the ReadWriteSdFat sketch is written and try to make those changes to my own sketch to see if I can read and write properly from the card.
If I leave the CRC check turned on, will this continue to be universally compatible with both these cards and other cards, with the speed penalty? I'm thinking with my relatively light needs, the speed penalty might be OK for this application.
Thanks.
-John