Hi Ray and welcome to the forum !
Not aware of any Ovni boats with an 100 % synthetic standing rigging, but could be wrong indeed. Cause didn't know it was cheaper over time than regular wire strand ? perhaps if you take care of all the fittings, lashing, etc yourself ?
May not be as expensive as some dedicated synthetic cable such as ECthree but you still need to purchase pre strechted heat set grades; see creep issues and am told it is not so easy to get to the correct shroud tension unless you have the dyneema ropes together with the final fittings pre- stretched. Rigging companies can cope with this , but i assume at an additional cost.
If you take care of everything yourself (heard it's possible/easier to adjust tension under sail) it offers one additional great advantage : easy to repair your rigging yourself even in the most remote locations, and not a weight issue to carry a few spare ropes onboard given the Dyneema light weight.
Cheers, Kev