tl;dr version: I inadvertently placed a Brown Dwarf near Sol in the wrong position on the Realistic Star Maps, which messed up the start of the French and Chinese Arms. But I’ve now fixed that and made a few other changes too, so be sure to check the updated pages!
The long version: A commenter here (thanks, Schutze!) pointed out that I’d made an error in the location of the brown dwarf WISE J1049-5319, which I previously placed at the start of the French and Chinese Arms. It turned out that I had used the Co-ordinate Converter from my Stellar Mapping page to calculate the location of that one system, but I’d forgotten to convert from the Galactic XYZ co-ordinates that it outputs into the Astrosynthesis XYZ format – so it ended up in the wrong place since everything around it was (correctly) in Astrosynthesis XYZ co-ordinates. There shouldn’t be any more errors like that in the maps – I’m pretty sure that was the only system for which I could have used the Galactic co-ordinates since everything else was converted using the Bulk Converter spreadsheet (which explicitly has Astrosynthesis XYZ columns that I copy the values from).
As a result, J1049-5319 was placed on the map in the wrong position, and fixing that really changed the start of the French Arm and somewhat changed the start of the Chinese Arm too. On the plus side though, the correct position of the J1049-5319 bridged the gap between Sol and Wolf 359 so that actually fixed that issue with the French Arm, and the new position also meant that the start of the Chinese Arm was more like it was in 2300AD canon.
Aside from the changes to the start of the French and Chinese Arms (involving the addition, removal and/or re-ordering of some systems), I’ve also significantly revamped Kafer Space by moving the Kafer homeworld to Psi Serpentis and adding a fictional Brown Dwarf between Psi and Lambda Serpentis, for reasons explained on the updated New French Arm page (it makes more sense like this now, and actually allows the Kafers to access human space!).
I’ve now updated the maps and descriptions on the New French Arm and New Chinese Arm posts, and also updated the Overview and Introduction posts to make all the preamble consistent (the New American Arm is unaffected by this, so it remains as it was).
So please be sure to check out the updated pages for the corrected information, and I’m sorry for missing that!