I tried using the new cr/lf line ending as documented:
set_line_ending Fixy::Record::LINE_ENDING_CRLF
And.... no change to the line endings. Looking into the code a bit, the line ending seems to be held in an instance variable and accessed from a class method, which could explain the problem... and I'm not sure what the intention was, so I'm reporting it rather than trying to fix it. Thanks!