Rob,
here are the sizes for the oval fingerboard inlays for the 8string neck:
3rd fret Length 2,2cms Width (at broadest point) 1,6cms
5th fret Length 1,8cms Width 1,3cms
7th fret Length 1,5cms Width 1,1cms
9th fret Length 1,25cms Width 0,9cms
12th fret Length 3,4cms Width 1,0cms
15th fret Length 1,85cms Width 1,0cms
17th fret Length 1,6cms Width 0,75cms
19th fret Length 1,25cms Width 0,7cms
21st fret Length 0,9cms Width 0,5cms
24th fret Length 1,2cms Width 0,4cms
Can you work with these?
Oliver (Spyderman)