AN better than SS
With my experience with giant scale RC and very large model engines (200+ CC), I can tell you that Stainless bolts shear very easily compared to AN bolts.
We had a number of guys shearing prop bolts (6) for no appraent reason. We kept telling them to tighten them appropriately. Later when they sent their engines to have new hubs installed, we discovered they had been using aftermarket Stainless bolts.