Purchasing a String Instrument -Sizing and Arching's

Many players don't like instruments with a high arching, as it will tend to produce a nasal quality, and will not generate the power of a good instrument with relatively flat arching. Higher arching was very popular in the Baroque era, where Stainer was the most notable violin maker. During the 1800s orchestras became larger, which created the need for more volume. The trend was to go to a flatter arching which helped produced this need for a big output in sound.

The next consideration is:

Sizing

Correct measurements are very important. Sticking to standard measurements will help greatly, particularly for intonation, if you play on more than one violin. (for instance, you have one violin for solo work and another for teaching, playing outdoors, etc.)  No set size goes with an age of a person. Not only does the length of the arm and fingers count but the strength is a factor as well.

For violas, the string length, like the body size, has never been standardized. There are some larger violas with a shorter string lengths, which might work well for somebody who has long arms and short fingers. Occasionally a larger nut can shorten the string length to accommodate those hands. I find that 15 1/2" up to 16" will generally work quite well for most viola players.