From my understanding this is a limitation on FlashRam itself. Flash Ram requires data to be erased in chunks which could span across multiple files or include only a portion of a file. My personal work around for this was to divide data up into multiple files, and make sure those files are created as "erasable" and use a wrapper class to handle the data in the files. If I need to wipe or replace data in a file, the wrapper class just copies all current data to ram, makes changes needed to the data, erases the file using SerialFlashFile.erase(), and then writes the new data back to the file.