noter/drone 6 string dulcimer players?
What Folkcraft says about their six-string is:
"When we string up six-string instruments here in the shop, we use two .011 strings for the melody course, two .013 strings for the middle course, and one .011 and one .024W string for the bass course".
"The melody strings are tuned in unison, the middle strings are tuned in unison, and the bass strings are tuned one-high (same as the melody string) and one-low (one octave below the melody string)."
I've played n/d on 3, 4 and 5 string dulcimers and I've borrowed a 6-string once in a while. I haven't felt the need to adapt my strumming except for one thing: how the number of strings (and how they're tuned) affects the sound balance between melody vs drones.
If you're used to a typical 4-string setup (with a doubled melody course) then you're used to hearing 2 melody strings and 2 drones. If you try a typical 6-string with three doubled courses, you'll have 2 melody strings and 4 drones. Which might seem like too many drones. If the drones are (ahem) droning out the melody then you'll want to adjust your strum. Angle the pick so you're strumming the melody string(s) harder than the drones. Don't feel compelled to strum across all the strings at every strum, either.
If you're used to a 3-string, then maybe a 6-string won't be a big change. There are a lot of possible 6-string setups and tunings. I guess the only real answer is listen while you strum and adapt as you like.
Not currently, but my second dulcimer, back in the Dark Ages, was a six string. Strumming takes a bit more 'work', but you can also get some subtle "brush strumming" using the pick on the first few strings and the edge of your little finger on the mid- bass drones as the hand rotates for the strum.
In general with doubled melody strings you have to make sure the noter is coming down dead-flat so that both melody strings are fretted equally rather than one fretted hard and the other one not so much. That leads to buzzy notes.