I've noticed that, more with the Firefly than with my old Stella, the way I hold the instrument changes the volume. I think I tend to hold the Firefly a little closer to my belly, thus muting it more; when I shift it away, the sound increases considerably. I think with the Stella, I play it more while seated, and therefore don't press it against myself - so the sound really stays constant. The skin head isn't as bright as the Fiberskin 3(tm) synthetic head on the Firefly either, but that's a non-issue - it is also probably the original head, and since the frets are pressed right into the neck, sliding isn't quite as smooth either. (But it is all original as far as I can tell, down to the rust.)
The more I play the Firefly, the more I like it. I think that if you want to aggressively strum, aka Formby Style, then you'd probably be better off with a more traditional banjo-uke with a resonator and tone ring, but that's just my opinion - I also prefer an open back 5-string banjo for old-time music, and a resonator-backed 5-string for bluegrass.
-Kurt