I don't know if this has been suggested already, but I thought of a potential workaround for those that need lower levels than the newer firmware can give you: use the DUAL REC function, with the second stereo track 12, 18, or whatever dB lower you choose. I do this all the time when I don't get a real level check and only have the one pair of mics going. I activate DUAL REC and set it to -12dB, and there's my safety tracks.
I'll be doing this tomorrow when I'm recording our 270 voice high school choir which can really crank, and they sometimes use a full orchestra or just a percussion section for parts of the concert. Since I never have a chance to go to their dress rehearsals to set levels ahead of time, and their dynamic range is huge, I'm going to go LOW gain about halfway up with the DUAL REC at -12dB. The safety track is pretty much mandatory for this concert.