I have to agree with Mandobart. I had a local luthier re-purpose a cheap old
Seagull Entourage Rustic Mini-Jumbo to an octave mandolin and it worked wonderfully. Scale is a bit shy of 25" and it plays wonderfully. It's a good match for my 23" scale Crosby custom-made "bouzar" (unison-strung octave mandolin based on a tenor guitar) but the longer scale of the converted Seagull -- and, let's face it, the Seagull headstock just cries out to be converted to an 8-string! -- allows it be tuned a 4th lower (so D instead of G).
Phil