I have built a hammered dulcimer over the course of the last year and it is 99% done. I have already performed with it and it worked nicely. However, I have some problems. I started building this instrument from a description of an Iranian santur which said to use three soundposts but the top started to sink in when I began tuning so I had to put in one more post. Now, I want to use a higher tuning, just like the santur, so I have bought new, lighter strings but the top does really not seem to like the pressure. Then I noticed a video of a Turkish santur which used a lot of supporting braces. I would think that having a hard support structure like that would diminish the sound but apparantly not.
So, what would you prefer to use and what would be the best way to solve my problem? I am already guessing that the sound posts are inadequate but I would like to hear your oppinion.