Actually no. I just swapped CTRNAND, AGBSAVE, TWLN, and TWLP of emunand with sysnand. (As long as the FIRM partitions aren't touched, A9L survives this). I had a 10.5 emunand. I basically just transferred that to my sysannd and used the 9.2 sysnand I had before as my emunand.
You have to swap the individual partitions though. Octopus Rift made the mistake of writing the entire 10.5 emunand partition to his sysnand. He ended up with a non exploitable 10.5 console.
Though he did manage downgrade it without a nand mod though. The details of which I'm not at liberty to discuss as the moment.