I’ve submitted a few observations to BeSS.
The good news is that the file format is identical to the BAA Spectroscopy Database format. They in fact came up with the format, and we used it as it makes sense to have one format across the different databases.
You can download spectra from the BeSS website, and on the registration screen there is a tool you can use to check your file.
The administrators are very friendly and knowledgeable, but note they can sometimes take a few weeks to respond.