Thanks John ---
(and THANK YOU to the keepers of the VNWA group to allow this conversation to continue, as it is somewhat broad-ranging topic at this point and references use of the HP 8753, APC-7, and HP cal kit); it does tie back to my VNWA 2.6 as that's the device I'll use once I get all of these cal kit parameter things understood!)
The Amphenol parts would certainly be quicker to source at this point!
I am having a hard time visualizing what leads to the negative delay on the 202114 male short and modified 031-320-RFX modified open... I understand that the reference plane on a BNC female is behind (away from the end of the outer edge of the connector), but the short (at least) has the physical short happening presumably near it's back edge (back cover), somewhat further out from the edge of the BNC female being "shorted", so I'd think intuitively that the delay would be a positive number. Understanding this will likely help me avoid gross errors as I consider BNC properties! So all that said, is there somewhere/something I can read up to understand the origin of the negative delay figures?