But, as it turns out - we did get more; two years' worth -
It just wasn't on Flint Baker.
Four months before Planet Comics #1 hit the stands with Flint Baker, Mystery Men Comics #1 premiered another planetary adventurer from Briefer -
Rex Dexter ran in the first 24 issues of Mystery Men, plus one issue of his own title - though that was mostly reprints. (On the other hand, when dealing with comics from 1939, reprints can be a nice thing to have around)
As you can see here, the distinctive stylings of his Flint Baker work are very present in Rex's strip -
Well, now i guess you probably want to see Rex in action, hmm?
I suppose we can manage that. But this post is fairly lengthy already, so - another time.
Meanwhile, here's a build-your-own Briefer style rocket kit:
art by Dick Briefer for Mystery Men Comics, various #s from 1-24 and Rex Dexter #1 (1939, 1940, 1941)