Are those the files that were used to produce the .ipq8074 files? I don’t think I’ve seen those *-reg.bin files on their own (which might be the issue). Any pointers on where to look or how to use them would be great.
As a quick test, I’ve just built the SXR code using a board-netgear_sxr80.ipq8074 that was copied from board-netgear_sxs80.ipq8074 (originally from your repo) but with the header changed from SXS to SXR in a hex editor. That did appear to work, with no warning shown on boot or switching the region. Haven't had a chance to check if the wireless side is all working yet though.