Daniel,
By way of update, I have achieved some modest progress on my issue with a manual workaround. I have elected to edit the enlightenment_theme_options manually. When I change the onecol grid option to twocol, the masonry grid is displayed in a two column format with the content-sidebar layout. Once I switch to threecol the wheels come off the cart. The display defaults back to one column in the content-sidebar layout. So, I attempted another workaround by changing the layout for full-width and unfortunately the default display with one column in the content-sidebar layout persists. Perhaps, my threecol syntax is incorrect. What should be enlightenment_theme_options grid settings be for a three column display with no leading posts?