I haven't got a copy of Elza's death certificate; but, will try to get one when I visit the State Archives this summer or fall. I loved the pictures you sent and will continue to try to identify the persons in them. April and I have been corresponding for several months and plan to meet in NW Missouri this fall. Maybe all three of us could meet in St. Joe and compare notes and pictures. I'll send you a copy of my family tree if you are interested and will give me your snail mail address.
Maybe the document I saw that stated that Eleanor was Elza's twin was incorrect. I found her mentioned in another place, (a census report I think); and she was mentioned as being a year younger than Elza. Elmer was not mentioned in that report if I recall correctly. That may have been the 1860 Census report that you referred to.
I'm planning a trip to Gallia County, Ohio, and Fayette County, Pa in a few weeks and will continue researching the Jefferson Harold/Thomas Jefferson Halfhill question. You might be right; Thomas Jefferson might be my great-great grandfather. I'll keep you posted on my findings.