I've found that I need to turn down the volume upstream of GigaPulse in some circumstances to avoid clipping. Turning down, say, the master output does not solve the problem.
This varies by instrument & impulse. Some instruments are just hotter than others. Also, a piano will often be the worst offender, because of all of the chords and poly that it produces. A solo oboe is much less likely to clip.
I've also had the occasionnal problem when instruments are loaded and re-loaded with program changes - especially instruments with built-in resonance (gsi files). Somehow things get doubled up in these cases. I haven't characterized exactly the behavior, but if you get clipping, and you're not sure if the performance is clean, it's best to reset and reload things. This is especially true if "it wasn't clipping a few minutes ago".
It seems to me that I've had some clipping problems when running GigaPiano II with resonance into a downstream GigaPulse for ambience. Things are just set too hot. By reducing the instrument volume just a few dB, the problem is solved.
Anyway, sometimes the problem is that the signal gets too hot, in other cases the problem is that the routing has gotten confused - especially with stacked resonance models (gsi) and program changes.