Jim,
Here's a thread I did demonstrating the M80...I've used it for years in my D18 because I did not want to alter it with a UST or SBT. Tho I'm mostly a MIJ Tak guy, I do use the D18/M80 for certain gig applications and recording. I think it's a fine pickup for what I do, tho it's not for everyone, but check this thread and vid out:
https://www.acousticguitarforum.com/...d.php?t=517255