wow took off for part of the day, came back and re-read what was posted earlier and saw I forgot one key point I had intended to mention in my response. Besides the possible middle name usage (re Eleanore/Kl�rchen), the other reason to be wary of assuming such things for appearance's sake is because of the high mortality rates of the past, and the arrival of new (and unexpected and otherwise unknown) spouses appearing in the records, be it male or female. If they happen to have similar or identical names, things can quickly go from bad to worse when trying to correlate the bits and pieces found in existing records. These are common trips from the past, especially when using sequential records like the censuses.
That said, Klarchen could be Eleanore as you suspect since things line up suitably, more so if Klara (or some variant thereof) happens to be her middle name (same scenario with Johann + Gustav btw). This includes the possible flipping of these names between christened and middle, unless something concrete indicates the actual birth name. Naturally your best bet is to attempt to locate some supporting documentation by way of additional references if possible (if not, one must rely on the preponderance of existing evidence and usage). As we all come to discover, such things are not always available the further back we travel, so you often assume certain things for the best when nothing else avails itself -- but should remain open to new possibilities should they arise.
Anyway, here's to getting to the bottom of such quirky sticklers. Best to remind one and all, not all family idiosyncrasies or "unknowns" are meant to be figured out. It is unfortunate but true -- all you can do is keep trying, the "pull" of research being the allure of discovery, to include the realization that some things will remain beyond our reach no matter how hard we try. "I guess it is one of those mysteries" is a rejoinder lamented more than most wish to admit.