I've got a pretty long wingspan myself and have wondered how the viola would feel compared to the violin.
Nice expression, wingspan.
I hope this digression doesn't bore people.
A lot of people have a bigger wingspan than they think.
Generally it's the same as your height, or maybe longer. The word fathom (6') is an Anglo-Saxon word meaning 'embrace'. It's four cubits (18" - the distance from your elbow to your fingertips).
I'm 1.67m and my embrace is 66". My teacher thinks I can handle a 16" viola easily, but I'll try before I buy, lol.