Comment:  An initial histogram skewed to the left (too dark) is fairly typical for scanning Kodachrome on the LS-2000.  In general, what you want is to have the left edge of the histogram abutting the left edge of the graph and the right edge of the histogram abutting the right edge of the graph.  Why do you want to do this?  The distance along the horizontal axis, from the left to right margins, represents the sensitivity range of the LS-2000, the scanner's D-Min to D-Max.  The idea is that the optimal use of this fairly limited range is achieved by mapping the image exactly over the available range.  Keep in mind that the ultimate output is a picture file of discrete (integer) values.  If you end up with an image which uses only, say, 180 of the 256 (this is relative) available tonal values your image will be more prone to posterization when the image is subsequently manipulated in an image processing program such as Photoshop.  That's the theory.  In practice I try not to place the black and white points so close to extremes of the histogram.  My rationale is that unless it's known that a real black or white is present in the image, it's more advantageous to have some leg- and head-room available for subsequent manipulation of the image.