Current build is on an Avo box with 25.5" scale and only about 16 frets, I usually tune to GDG and get a wide range of notes high to low.
I assume this shorter neck tuned GDG will be a more bass tone, can it be tuned differently to compensate slightly so its closer to a longer neck sounds across the strings?
The number of frets and/or length of the neck doesn't change anything... it's still 25.5" scale... same tone if you use the same strings tuned to the same pitch.
+1 on what Korrigan said. Are you saying you want a brighter tone, as in tuning up. You can always tune up to AEA from GDG or you can switch over to D/G/B strings. That gives a brighter tone banjo like tone, especially on the upper frets? Since you’re tuning to GDG, I assume you’re using strings A/D/G? Do you prefer more frets. Does the neck have a separate fretboard, you can always replace it with a longer one or blend in an extension between the 15-16th fret. Maybe some more info would help?
Yep as the guys above say......or you could try what I do, use a capo.
1]You could tune to concert with the capo on
2]remove the capo for lower tones
3]move the capo up for a higher tones
I'm also thinking that the scale difference on the same box with the same gauge string will give the same bass response. Going shorter means strings will need less tension, so going to heavier strings may give more low end.