split backstays

[osteoderm]

If this is one of those topics that has been over-discussed somewhere, i sure haven't read about it... yet.
My double-ended boat has a split backstay. The plate connecting the lower legs to the upper leg is about 8" above the deck. There are no adjusters other than the turnbuckles. My question is a general one: What is the optimum height above deck for the join, or better yet, what is the optimal angle off vertical of each lower leg? It's not applicable to my relatively narrow boat, but at what point of beaminess aft is it better to go with dual backstays rather than the split (assuming that a single central backstay is somehow otherwise undesireable, say, in a boat with a wide swim platform like Beneteau 42, etc.)?

Thanks,

Yuri