OK, thanks to **KrazyHorse**'s suggestions, I tried some radical "cranking up" of the power settings for the skydome in the Worlbase XT set, and was able to produce the render above.  I turned the Sky dome to a light and set both Gain and Power in Reality to the maximums, 10,000 each.  I also have a typical two-light Main/Fill mesh lights set to light the figure.  The Main was set to 5,000 Watts and the Fill to 2,000 Watts.

I found that even with the Reality settings above, I still had to adjust the Sky light upward in Lux.  I dropped the Main and Fill slightly also.  Love those separate light groups!  It has been baking for over 9 hours now, reaching 350 S/p.

  ~ Russ  (a.k.a. Ansel)