Having found that nylon is kinder on youngsters’ fingers than gut, and they still get sore when they don’t practise enough, what’s your view or feel on the fluorocarbon option, as I suspect the fluorocarbon is rougher than simple nylon ? Presumably the fluorocarbon gives a more realistic tension as an all nylon lever harp is a little low in tension even for youngsters. I do have small harps with each type but it’s a matter of passing on advice to new parents/pupils.
I find fluorocarbon strings, or rather, Savarez, painful to play. They are much tighter. Pirastro makes the best nylon strings, if only because they are a bit thicker. I believe they are now made with the same material as other nylon brands, but it used to be something more durable.