Searched through all Lite options, Pro options, LR export plugin options, and I cannot find a means to display proportional thumbnails on a Juicebox gallery.  I can set all of them to a particular proportion, say 75px x 50px, but if I display both horizontal and vertical images in one gallery, one or the other or both will be cropped to whatever I set in the options.

Say it isn't so?  Am I the only one who requires this functionality?  Or, as is more likely, am I just blind and can't find it?