Food for thought.
For your PRS-350s you might consider the following plugboard. This puts the series info on the author line.
Code:
Format: device_db
Device: PRS505
Source template: {author_sort} {series:| - | } {series_index:05.2f}
Destination field: authors
Source template: {author_sort} {series:| - | } {series_index:05.2f}{title}
Destination field: title_sort
I attached the plugboard image and a screenshot of how it looks on my PRS-950, but I use the same plugboard for my son's PRS-350 and it shows the same.