Complex sentence: At lunar perigee the tidal force is even stronger, resulting in perigean spring tides which can be slightly higher and lower; but even at its most powerful this force is still weak causing tidal differences of inches at most.
Split into simpler sentences: At lunar perigee the tidal force is somewhat stronger, resulting in perigean spring tides. But even at its most powerful this force is still relatively weak causing tidal differences of inches at most.