I came to my own rescue this morning. I couldn't recall how to properly generate efficiency histograms in ROOT using weighted data (in 5.30, ROOT doesn't allow that in TEfficiency). So I duck'ed for a solution (https://duckduckgo.com). Past me came to present me's aid: http://steve.cooleysekula.net/goingupalleys/2011/08/09/python-and-root-tricks-efficiency-graphs/