Hello Ripton and others.  Most luthiers believe that a ratio of 1:6 between the after length (bridge to tailpiece) and string playing length (nut to bridge) is ideal.  Various things can be done to influence this ratio.

The most obvious and immediately advantageous is to remove the fine tuners (perhaps with the utilization of a piccolo tuner on the a string of the viola).

Adjustment can be easily be made on the tailpiece gut to affect the distance between the saddle and the tailpiece.

Additional lower harmonics can be obtained by the use of a “harp” style tailpiece and by the use of intentionally smaller tailpieces (such as the use of a 16” tailpiece on a 16 1/2” viola).  I frequently use a 3/4 tailpiece on a 4/4 violin.  The latter practice is similar to the continental “Senza System.”  It is very effective on warming the sound of a harsh instrument, but can be over done.  I have an interest in this and have frequently done it.

Lastly, although not strictly germaine to this discussion, is the material used for the tail piece.  Ebony, rosewood, boxwood, aluminum, carbon fiber and plastic have all been employed in useful tailpieces and all offer different sounds to the instrument.