Haha, my recent meer had a 9mm filter. This is all anecdotal and personal, but perhaps it will add to a data point. I absolutely love the balsa filters.
I’m not going to get into the science behind them, as frankly, I’m a little skeptical, but, they do filter, and if they don’t come close to their claims I believe they’d be liable to some lawsuits, although I’m not sure about that.
All that being said, concerning the smoke itself, I’ve found a slight (very slight) “shifting” of the flavor, but no reduction in taste. For me, it’s as if you were listening to music and adjusted the ranges a bit differently. Furthermore, any irritation in the back or roof of my throat/mouth virtually disappeared. I sip my tobacco, and smoke slowly, and to be honest, never really noticed the irritation until I tried the filter.
I’d second the cob with a 6mm as a way to test this all out. If you’re like me, you’ll love it. If you’re like all these other curmudgeons (spoken endearingly) you’ll return to this post and request I pay your 12 cob costs. Best of luck!