Before answering any questions take this into account, the instrument is home made and very similar to a banjo, but not a traditional banjo:
1. What causes overtones or too much tone?
If I play a chord it sounds like the chord is out of tune but each string is really in tune.
The bridge is in the correct location (checked the 12th fret harmonic).
I have tried many different tensions on the head, from hardly any tension to extreme tension and everywhere in between. The tighter the head, the more excessive the resonance, but it does not change the fact that a chord sounds off.
2. The tailpiece is not traditional (picture an acoustic guitar saddle attached to the back of the hoop and you'll get the idea). Could this be the problem?
3. If the tone ring is slightly out of round would this cause major overtones?
4. If the bridge is completely flat on the bottom side (I haven't cut it yet), would this cause major overtones or excessive resonance?
If all of the above are a major factor, which one would you start with? Which one would you correct first?
Thanks.