I'm another 5 string frailer, and another fan of Patrick Costello. It was mainly his blues playing & instruction that initially appealed, but when he says "As a frailing banjo player I have been able to take part in a pretty freaking huge range of music" - well, amen to that!

I also play tenor (in CGDA tuning) which I took to like a duck to water from mandolin playing.

Thread drift - viola not common in folk - why not?

Pete.