Unpaid Beta Testers! No really I do appreciate you doing this. The only other thing to do is to try and split files that need separate loadings.
I also did think of adding voice to the wavs (maybe a -v option to repeat the filename in voice form) but it gets quite cumbersome for a command line app, didnt really find a library but I did put together a set of pre-recorded wav file of letters and numbers using
https://cloud.google.com/text-to-speech.
Maybe I could just concatenate a few of those into the wav before the data stream, ive added a sound file to see what it would sound like. Its not quite Joanna Lumley!