Hi Jeff,
Whatever you do in Refine, QU "smart" raw processing gets the extremes of the histogram right in most cases. The exception seems to be when some highlight recovery and/or or HDR is required which sorts out the right hand end of the histogram. Fill then moves any "bulge" at the lower end towards the right. However, I rarely need refer to the histogram in the editor because the refine process is "smart" and a visual appraisal, together with a RMB to check RGB values in the Refine Screen is usually adequate. They are my observations on the matter fwtw.
Terry