Fast loading of the native *.FVX file:  98% of time is spent in   DCMTK::FindTagName function.
After call parallelization, interestingly, execution time has doubled.  Looking into resolving this to achieve "more instant" load.  Presently it is about 10 sec for 300,000 slice volume.

Result:   "Native" loading of the original DICOM 5.6GB dataset is now 0.7 sec.