If your ram needs 1.87 (Not all 1.8 ram will) then you will need to raise your QPI to at least 1.3-1.35.
That would likely help you with stability anyway at 190 bclk
To answer you, no that is not safe to run your ram that high with QPI that low.
Here is a Thread at XS that has some discussion on this subject >>>
Core i7 Vdimm/VTT Graveyard :D - XtremeSystems Forums