I heard the pilots in those carried these for a sidearm:
Your post is exactly what I thought of when I read the article!
For no good reason, a couple of weeks ago I got interested in the Twin Mustang and did the usual amount of superficial research on it. Including one guy who found one and refurbished it. He said that between the F 82 and the Mustang that there are about 14 parts that are the same. And over 10,000 that are different.. they share practically zero Parts in common.