Hi. Don’t know if this topic is still of interest, but I’ve played two different “full” sizes in the 23 years I’ve been playing. For many years I played a 16″ instrument because that was the more acceptable full-sized instrument, and also the one that has the most variety of choices from makers. There’s also a bit of an old school/new school thought process in terms of what measurement of viola one should play. The old school approach is to play the largest instrument you can handle because the bigger ones are the ones to produce that more “viola-like” deep quality. However, the unintended consequence is over extension of forearms, wrists, and hands. Now, there’s a definite disconnect with this approach. If you played a chin instrument as a child, you probably remember being sized for your violin or viola by trying to reach out and wrap your hand around the scroll. If you can’t reach, or your arm was over-extended, that meant the instrument is too big for you, and will cause issues with comfort and ability to play with proper technique. Why shouldn’t this apply as an adult? Why keep going for the larger and larger violas (supposedly for the biggest sound) at the expense of technique and potential wrist injury? That’s where the “new school” approach comes in. Personally, I’m a shorter-framed person who really had no business playing on a 16 ” instrument. Over the years it caused me to suffer from some pretty bad tendinitis – especially when performing longer stage works in the pit. I ended up needing to take a hiatus from regular playing because it became so uncomfortable. This brings us to more recently, when I’ve since resumed playing, sold my old viola, and began performing on a 15″ viola. The act of playing and practicing is so much more of a joy. That, and size shouldn’t ever be a factor with viola tone if you’re playing on a well-made instrument!
Sorry about such a long post. I suppose the short version of my personal journey is, if you’re concerned about getting a rich viola tone, don’t sacrifice your personal health. Instead focus on finding the right, well-made instrument that fits the bill on both fronts.