I have a few sets of Kala Red for soprano and concert. They didn't work well on my Bushman Concert Jenny (Aquila is best for it). But they worked well on an old Decca Soprano and on my Northern JCD-2 concert - and on my plastic TV Pal! The wound C string broke the plastic friction peg tuner on my TV Pal, but I put in an old tuner and the strings sound great. see my videos for what they sound like - Hank Snow song with the strings on my Northern. And Deep River Blues in my garage for the TV Pal! Oh also, the Advantage to playing ukuele that I also did in my garage. The reds strings on an old Decca that I painted baby blue!
Hope that helps!