The cemetary near the Matilda Champion house is undoubtedly where their mound is located. However, this doesn't match the description offered: "fired into [Champion Hill] from the west." The cemetary on this map is north-by-northeast of Champion Hill.
Maybe you call this "nitpicking" but I think placing Hovey's guns this far back perpetuates a meme that misrepresents what happened at the battle. The Confederate high tide ebbed on top of Champion Hill, not below it. Holmes and Slack's remnants had a nearly unassailable position, and Boomer's final wheeling movement had refused the federal flank in the other direction. Hovey's batteries guaranteed that the Confederates could not slip into the space between the two, so the Confederates really had no direction to move but retrograde.