I think I would like the turnbuckle also, but I haven't tried to adjust my diamonds yet. They are set up with the threaded end through the mast plate with a nut on them. I don't see how it would be a problem. Is the mast plate stainless on the blades? Can't say for sure.
I know the Blade manual recommends lubing the nuts on the diamonds due to the "cold welding" issue.
I will post a pic later