I thought the size limit was more like 50kB?
If you connect the PSR-E403 to a computer, iPad, etc., you can have a DAW or other MIDI software play MIDI data to the keyboard. And you might even be able to find a program that can play and control Yamaha style files similarly to the way that you'd play them on the keyboard. But you'd probably have to control the style playback from the computer software or iPad app.