Swap would be fine for button 5

P1B1: (SELECT/FIRE)
P1B2: (SPACE)
P1B3: Save Snapshot
P1B4: Warp Mode
P1B5: How about Swap here
P1B6: Load Snapshot
P1B7: (How about RUN/STOP)?
P1B8: (How about PAUSE or MENU)?
P1B9: (Quit) (Or do you just want MENU then let the use select QUIT in case of accidental push?)

Menu is fine, or let me know what the quit option is so I can try it.

Many thanks mate!