Suggested edit: I'm requesting a change to his middle name because
(1) no middle name or initial appears on the stone . When added from other sources, it has to be irrefutable - and it's not.
(2) there is direct evidence for a middle initial ("L.D" in 1900 census, "Lewis D" in 1910 census.)
(3) but there is no direct evidence for a full middle name (that I'm aware of)
(4) the middle name seems to be inferred from his son Lewis' middle name, but that is not always a safe inference. (For example, my mother is Donna Joanne, but I was named Donna Janeen - but changed spelling to Dawna at age 16)
(5) even the son's middle name is not definitely established. It is Dunkling on son's death certificate. But they are notoriously inaccurate as the info is second-hand while grieved. Son's middle name also appears as Duncan (1880 census) and Dunkan (1910 census).

Family researchers are split on the issue of the son's middle name. Some have taken it directly from the dubious death certificate, but most presume that Duncan is more likely correct, but became corrupted over time.
So, because the middle name is not actually carved on the stone then it should be left off. Or just show middle initial D with the explanation above. By adding a full middle name that is not on the stone - you turn conjecture into fact and the middle name "Dunkling" is not actually a fact.
Contributor: Dawna (46875402)

Contributor Jim Hightower (47966559) states:
Another member states that the middle name might be "Duncan" and seems to have more than "said-to-be" documentation to support that statement.
Lewis' son is buried in the same cemetery and his grave-marker reads Lewis "Dunk" Abercrombie. I suggest that "Duncan" be added into the father of Lewis, Jr.'s name or at least put in the notes.