If the tires are rated to 50 PSI, there is no reason not to go all the way up to that pressure. The end point should still have little margin, and you may be able to go even +5 or +10 PSI (do at your own risk), but be aware that the pressure could go up if the tire gets very hot (sun, or heavy braking on long, steep hills).

2.3" tires sound awfully wide to get pinch flats, but I suppose it depends on what you're rolling over.