In My brief experience as a student of the CG I have researched,read about,and try-out several guitar sizes and have arrived to the conclusion
that the most neglected phase in choosing a CG is the scale-length(string distance from the Nut to the top of the saddle).
Not everyone-regardless of age or stature- have
fingers that can confortably play within the standard 650mm CG fretboard.
Most of the CG in the market place today are manufactured(unless is a luthier-made instrument)with the "standard" 650mm scale length.
This is one area where the old saying "No pain No gain" does not apply.
Some new students of the CG arrive at a point of
almost given-up the instrument if not for the
"discovery" that a shorter "scale-length" guitar will eliminate the disconfort and begin to see
positive progress in their study of the guitar.
Remember that the music for the classical guitar written by composers like Sor,Giuliani,Carcassi, etc.was played with instruments with scale-length shorter that today's 650mm "standard".
There are today some "factory-made" CG that can
be available with scale-lengths from 610mm to
635mm, Some manufacturers use the term 7/8 size
or even 3/4 size when describing these guitars.
The important factor is to determine the exact
scale-length.
As a reference: 1.0 Inches = 25.4 millimiters
A 650mm scale length = 25.6"
