The shitgibbon definition is surprisingly specific about the metric composition of the pejorative compound, indicating that it must be antibacchic, which means

The shitgibbon definition is surprisingly specific about the metric composition of the pejorative compound, indicating that it must be antibacchic, which means two stressed syllables followed by an unstressed. So "assmonkey" and "twatwaffle" fit the bill, but common forms such as "asshat" and "dickwad" do not.