After I wrote and posted about Todd Phillips' archtop guitar to mandocello conversions, I remembered that Frank Ford described converting a Martin 000-15 to an octave mandolin on his Frets.com website.
Here's the guitar before it was converted:
1999 Martin 000-15
Here are a few photos he took after he finished the job:
1999 Martin 000-15 Octave Mandolin Conversion
Here's the full article for those who'd like to read it for themselves:
http://www.frets.com/FretsPages/Luth...stconvert.html
Here's the index page for Frets.com, which is a labor of love by Frank Ford and really an invaluable resource for anyone interested in the technical aspects of fretted stringed instruments:
http://www.frets.com/FretsPages/pagelist.html
Hope this helps.
Wade Hampton Miller