I didn't have any detailed analysis done for the Retro-Hugos this year, but I did vote (I have read them all -- all the short fiction, that is) ... Here's how I voted:
2 Coventry by by Robert A. Heinlein (Astounding Science-Fiction, July 1940)
4 If This Goes On... by by Robert A. Heinlein (Astounding Science-Fiction, Feb 1940)
3 Magic, Inc. by by Robert A. Heinlein (Unknown, Sept 1940)
1 The Mathematics of Magic by by L. Sprague de Camp and Fletcher Pratt (Unknown, Aug 1940)
5 The Roaring Trumpet by by L. Sprague de Camp and Fletcher Pratt (Unknown, May 1940)
Comments: I liked The Incomplete Enchanter quite a bit, so I voted the better half of it first. Then I figured I'd list the three Heinlein stories ... I could have put them in just about any order. And the rest of The Incomplete Enchanter went last.
2 Blowups Happen by by Robert A. Heinlein (Astounding Science-Fiction, Sept 1940)
No Vote XX Darker Than You Think XX by by Jack Williamson (XX - NOT ELIGIBLE)
3 Farewell to the Master by by Harry Bates (Astounding Science-Fiction, Oct 1940)
5 It! by by Theodore Sturgeon (Unknown, Aug 1940)
1 The Roads Must Roll by by Robert A. Heinlein (Astounding Science-Fiction, June 1940)
4 Vault of the Beast by by A.E. Van Vogt (Astounding Science-Fiction, August 1940)
I've never really liked Sturgeon's "It" that much, so it went last. I could have voted the Heinleins in either order I guess, I went with the one that had the more immediate impact on me when I first read it, though that might only have been because I read it earlier, in The SF Hall of Fame.
This does illuminate a problem with the Retro Hugos -- the nominators somehow placed Jack Williamson's "Darker Than You Think" -- which I think of as a novel, but might be short enough to qualify as a novella -- in the novelette category. It actually would have been a much better Novel nomination than Williamson's all but forgotten, and not all that good, The Reign of Wizardry.
Best Short Story
4 Martian Quest by by Leigh Brackett (Astounding Science-Fiction, Feb 1940)
2 Requiem by by Robert A. Heinlein (Astounding Science-Fiction, Jan 1940)
5 Robbie by by Isaac Asimov (Super Science Stories, Sept 1940)
3 The Stellar Legion by by Leigh Brackett (Planet Stories, Winter 1940)
1 Tlön, Uqbar, Orbis Tertius by by Jorge Luis Borges (Sur, 1940)
This one was easy: "Tlon, Uqbar, Orbis Tertius" is a great great story, one of the greatest SF stories of all time. Of course, it wouldn't have been nominated in 1940, if only because it wasn't translated into English until much later.
I listed the Heinlein (which will almost certainly win) second, and the two Brackett stories next. They are, I think, her first two stories, and they are good enough, I suppose, thought not close to as good as her later work. I've never much liked "Robbie" -- it is remembered, I think, only because it's Asimov's first Robot story.
I think it rather likely that Heinlein will sweep the short fiction categories.