Bob,
I'll try to provide some answers.
1) Railing Specs. I can't be of much help. I have some info for FLETCHERS but next to none on SIMS class. Stanchions used were "standard" types ... lots of types for all kinds of locations aboard the ships. "IN GENERAL" it looks like the deck edge stanchions were ABOUT 3.5-ft tall and stanchions on inboard deckhouses were ABOUT 3-ft tall. But, there were exceptions all over the place.
2) Aft Con Station. As best I know, there was only a compass and communications equipment with the engine room and emergency steering below decks. This is as good a place as any to mention that DEPENDING on when ... timeframe ... AND WHICH sub-group of SIMS class destroyers you are modeling, the aft con station was located in various places and had slightly different configurations.
When the war started "officially" for the USA on 7 December 1941, the SIMS class appears to have been in a minimum of THREE Configurations. The nine units heading for the Pacific from the Atlantic Fleet were from one DesRon unit, but they were quickly updated with revised layouts and had 20-mm guns installed in place of 50-cal MGs. But, they were divided into two groups based on which yard they were modified at;
Norfolk Navy Yard group retained a small deckhouse atop the aft main deck deckhouse. The aft con station was atop this small deckhouse at the far AFT edge.
DD-409 SIMS
DD-410 HUGHES
DD-414 RUSSELL
DD-415 O'BRIEN
DD-416 WALKE
Charleston Navy Yard group did away with the small deckhouse and installed the aft con station at the FORWARD edge of the aft main deck deckhouse.
DD-411 ANDERSON
DD-412 HAMMANN
DD-413 MUSTIN
DD-417 MORRIS
Then there were three units assigned to different DesRon that remained in the Atlantic. I don't know at this time what configurations these three had and when and for HOW long.
DD-418 ROE
DD-419 WAINWRIGHT
DD-420 BUCK
You have asked about the SIMS group, I don't know if that is your solo focus or not for your CAD design. The two groups in the Pacific stayed pretty much in the same configurations until after the Battle of Midway. After which, modifications varied for almost ALL of the surviving units until the installation of two twin 40-mm mounts "sort" of standardized everything ... sort of. The variations depended on when and where top-hamper was removed and in general two 20-mm guns were added.
I don't have any image looking directly at the aft con station equipment for ANY of the Norfolk Group. Here is a view from forward looking at the location. Also here is a 1945 overhead view looking at the aft con station on MUSTIN in 1945. Without any other info to go on, this should be representative of these stations.
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MustinAftConStation-1945.jpg [ 139.18 KiB | Viewed 2744 times ]
3) View of the aft end of the aft deckhouse. Here is about as good as I can get. The 54 mount kind of gets in the way.
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OBrienAftDeckhouse.jpg [ 109.42 KiB | Viewed 2744 times ]