Thanks for the recommendation. I saw a rec for -12 so it sounds like that range is in the zone.
I have mine set at -18 and have clipped it a few times for s split second here and there with it typically peaking around -6 to -10
Fast peaks will not register on the meters as they are VU / RMS rather than peak (PPM). How much extra headroom you need to leave will strongly depend on the crest factor (peakiness) of the music you are recording. Used on stage near drums (high crest factor / more extreme peaks) you'll need to shoot for a lower level on the meters than you would when recording from a more distant position out in the room where peaks will be less extreme, as long as the PA is louder than nearby applause. Nearby applause is pretty peaky.
What gain setting you need to use to achieve that will depend on the sensitivity of the mics you are using, or the output level of an external preamp if used.
[Edit- I'll be pleased if firmware updates provide the ability to switch metering to PPM to better catch the actual peaks.]