aysvideo, we've been discussing this here on the board and share your concern.
The highest signal level that any recorder is capable of passing or recording without clipping or a exceeding a certain level of distortion is determined by the available analog input headroom of the recorder. It is this maximum input level spec that is of interest in regards to your question.
Referring to dogmusic's comment- Any particular recorder may be or may not be designed so that one needn't worry about setting input levels as long as the input does not exceed the maximum input level, but the signal needs to "get into the box" without overloading the input before that can happen. Mixpre-II series and all other 32bit floating point storage recorders are no different in this regard.
I encounter the problem you ask about when using hot output condenser microphones when recording loud amplified material into an F8 (not N). I am using phantom power from the recorder to power the microphones with no external attenuation, and find I need to engage the advanced look-ahead limiter to avoid clipping. Unlike the F8, the F8n is capable of providing phantom power in line-input mode, and line-input mode reduces minimum input sensitivity a further -10dB over that of the mic-input. I speculate that would take care of the problem for me, however it would be better if the mic-inputs of both units were capable of accepting hotter inputs without the limiter engaged.
Here are the specs quoted from the manuals (Zoom) and website (SD)-
F8 mic maximum input level (XLR, phantom available): +14 dBu (at 0 dBFS, limiter ON)
F8 line maximum input level: (TRS, no phantom available) +34 dBu (at 0 dBFS, limiter ON)
F8n mic maximum input level (XLR/TRS combo-jack, phantom available): +14 dBu (at 0 dBFS, limiter ON)
F8n line maximum input level (XLR/TRS combo-jack, phantom available): +24 dBu (at 0 dBFS, limiter ON)
SD MixPre-II mic maximum input (XLR, phantom available): +14 dBu (limiters on or off)
SD MixPre-II line maximum input (XLR, phantom available): +28 dBu (limiters on or off)
It appears the SD mixpre II series is able to handle similar mic-input levels as F8/F8n, yet without the limiter engaged, and somewhat higher line-input levels (with phantom) without the limiter engaged.