Hello Ian!I just wanted to say that Beethoven's Waldstein Sonata is a very challenging piece, so I congratulate you on your accomplishment in learning it. The triplets from bars 344 to 378 are fairly difficult to play at first, but once you practice this section slowly and with a metronome for a few weeks, or even days, it'll feel fairly comfortable in your hands, if you have any trouble with fingering, just let me know. Although it can be considered the most difficult part at first, it became the easiest for me after completing the piece, generally, I believe the hardest thing to do in this sonata, (and really any) would be to bring out the melody at the beginning of the movement and throughout the piece.