Maybe it's just my ear, but since I built my own MD, I have decided that the string placement/order on the MD is superior to that of a stick dulcimer (strum stick, strummer, call it what you like). When you do a "down strum" on the stick dulcimer, the strings are struck in this order: bass, middle, melody, but on a MD, with the equivalent "out strum", the strings are struck in this order: melody, middle, bass. The result is that you can hear the melody a bit better (clearer) because it is sounded first. This also makes the notes of the MD drone sound a bit clearer (and sweater IMHO).
On my McNally strum stick and the stick dulcimers I've built, there always was a problem with the drone strings drowning out the sound of the melody. On my earlier instruments, I tried to fix this problem by adding a second melody string (and then a second middle string for those songs that use the second string for a few more low melody notes - because the transition of 2 string notes to one string notes was too bad sounding; and I finally gave up because all this was doing is leading me down the path of doing a 6 string instrument with all three strings paired (and the melody would be drowned out again). Now, since I've been playing with my MD, I think the problem is basically string order. If the melody string is sounded first, then you can hear it a bit better, rather than having it drowned out by the middle and bass strings.
This could be resolved in two ways: (1) change the string order on stick dulcimers, or (2) instead of playing with down strums, change your playing style to use "up strums" instead. While this second way requires no modification to the instrument, it's pretty hard to break the old down strum habit. But, if you were to change the string order on the stick dulcimer, you would also have to modify your fretting hand style, since the top string (the one closest to your nose) is now the melody string and to play your melody you have to reach over the bass and middle strings (may not be so easy, but it would allow you to continue to play with a down strum using your other hand).
Any thoughts or comments?
Maybe the answer is to learn how to strum down and up, which fixes the problem half the time and may be why no one has noticed or complained about this problem before.
I moved down again to 26/17/13 strings and it is much, much, better.
On my next I'll use two melody strings 22/14 (12/12) and see how that works.
Another "trick" I leaned from a Balalaika player in a similar discussion on the Internet is to use nylon strings (from a classical guitar or ukulele string set) for stings 2 and 3 (the two drone string), and use a standard steel guitar string for the melody string. The idea was that the steel melody string would ring out more than the nylon of the melody strings. I tried this on one of my stick dulcimers, and found it is true, but IMHO I thought the nylon mutes the drone a bit too much, but since that time it has "grown on me" and I rather like this solution. Give it a try and some time to see if it grows on you as well. The Balalaika player recommended some brand of classical guitar strings (which is what I bought), but I have since forgotten what brand they were. However, the strings are gold in color. I also used the same gauge for the nylon drone strings (as Balalaika players string their instruments), but tuned it to DAD'.
My newest stick has dulcimer strings and it sounds balanced to me, it's acoustic only. The two melody strings seem to hold their own against the larger strings. Scale is 25", tuned DAD. I'll get a video up when I'm done tweaking.
Uploaded a video of my latest stick dulcimer and I don't think the drones are drowning out the melody strings but tell me what you think.