How you could have heard of him: Beyond his Who's Who appearance (and the usual cameo in History of the DCU that usually produces), Hop's only appearances after the 1948 were in G.I. Combat #152 (1972), a strip in which in shoots a lot of Japanese soldiers to the "tune" of the 23rd Psalm, atypical of his stories, but written and drawn by Jon Blummer (with some help from King David, I guess); and a couple issues of Young All-Stars.
Example story: All-American Comics #48 (1943) reprinted in America at War: The Best of DC War Comics (Simon and Schuster, 1979)
Despite his multi-media popularity at the time, Hop soon faded from our thoughts and comics, leaving the skies to other aces like the Blackhawks and the Silver Age of capes. Would he still be around if he'd gone costumed hero? Turns out he did, twice:
Who else? One more from Who's Who vol.X before we hit the "I"s and "J"s...