Usually run Speed Kings and Bontrager ACX's at 40psi. Did a race though a couple of weeks ago and had a tubeless blow-out owing to a cut – however managed to stuff just enough air in to keep going once it sealed. I didn't bother about the pressure, just straight back on as soon as it stopped hissing and had a tiny bit of pressure (was on last lap). I was astonished at the extra grip and it still rolled well, as well as not being flung in the air all over the roots – really made me think I should drop my pressures a fair bit. I checked it at home on the track pumnp and it read somewhere a bit below 20psi.
Never really thought to experiment with pressures, have only just gone to tubeless and still in the pinch flat mindset.