On Wednesday, February 26, 2020 at 3:21:55 PM UTC-5, Papa3 wrote:
I know there are a lot of threads regarding conversion of .IGC to .KML format, but does anyone know of a tool to go the opposite direction. Obviously, some of the header records etc would need to be "dummied", but I'm only really interested in being able to step through B Records using SeeYou or another igc viewer.

Have you tried gpsbabel?

https://www.gpsbabel.org/capabilities.html