Kalita "Kantan" Drip Brewer

If you haven't seen them, here's a pic.  They come from Korea (the packaging and brew instructions are in Korean).
First attempt I ground to about the same as I would with the Hario V60, since they're both drip methods. The result was a very slow extraction and quite a strong coffee - not quite bitter but certainly not to my taste.  I used around 20g and 300ml of water, which turned out to be too much grinds for the size of the kantan's filter basket so I couldn't fit it all in, and that also made the pour difficult as it was spilling over.  Eventually it clogged too.  The paper filter is quite dense, it seems, so I need a coarser grind.

Second attempt I went for 15g and 250ml. I also changed the grind to coarser... 15 on the Gaggia MDF...a little finer than French Press. Result = Better. 30 second bloom, 2.5 minutes extraction time.  Tasted ok, definitely acceptable - yet not brilliant.  I was using El Salvador Finca Argentina (Washed), which I've been having in a French Press and getting really zingy citrus notes, yet the kantan seems to have chopped the peaks off and made it somewhat unremarkable.  But for now I'll hold up my hands and say that it's quite possible just that I need to tweak my kantan brew technique... I could do more things with the dose, grind, pour technique (the rectangular basket suggests to me that the usual circular pour isn't the best way to get an even extraction), temperature.  I'll get around to reading of Scott Rao's 'other' book one of these days! It'd be good to have a clue what direction to go in with my tweaks.

On reflection, I like the kantan but it has made me start questioning where the line is between a good drip filter and a tea-bag/pod for coffee.  I suspect that a lot of research and development has gone into the kantan filter paper regarding particle size filtration etc, and I wonder if there's any info out there - or comparison with other filter papers such as the V60 or Chemex.