Here's a simple template I made to fret a 26-1/2" VSL with 18 frets for a recent build. It's a chromatic scale, no problem for guitar players.
Just print it, cut it, overlap the marked frets, and mark up your fretboard.
Here's the PDF for most printers... 26 ½" VSL 18 Fret (Letter Size)
...and if you have an 11 x 17 printer: 26 ½" VSL 18 Fret (Tabloid Size)
This works great for me - I'm making more for my favorite setups.