Hey, Just heard - they've arrested the quilt police for impersonating an officer! No, really!!!! We are Freeeeeeee to do whatever we want!
The only thing "magic" about 6" is that's the width of the first rotary cutting rulers. The other widths came later.
When I am putting borders on my quilts, I add one, then stand back & decide if that's the right size. I repeat until I'm done. I re-did the coral border of my avatar quilt as I had one too big on there first. cut it down nearly in half! This is the first time a quilt has spoken to me. If they're talking, I'm not usually listening! :-)