Hi Chris, I have a viola but haven’t played it recently. I am pretty sure it’s a full size viola. I used my violin playing knowledge/skill to transfer to viola playing. I played viola in a youth symphony (as a teacher / helper) some years back, since they had a shortage of viola players then. I found the alto clef to be a pretty good challenge, mentally. I really had to work at it, at first. Once I played viola regularly, my mind made the switch fairly easily. Now that I haven’t played viola for a long time, it would probably take regular practice to get comfortable with the clef. But as far as the physical differences, I never really had any issues.