I don't believe Extra Encore Stage is available - unless I'm not playing a song that is required.
Overall I'm having a lot of fun with this! I did fix my issue with it defaulting to showing the Calories screen (modify ddr_16_profiles -- Should_Display_Weight = 0 in the "butterfly.sqlite" database). so now it defaults to showing judgement. Wish we could have it remember the unlocked songs that appear when entering your card PIN as well as disable the "Grand Finale" screen at the end of each song, but those are minor quibbles for a game that's working perfectly otherwise.
I just miss the DDR Extreme interface for the arrows! (I think they're slightly smaller than the A20 interface - just found I can read things faster/easier if I pick one of the DDR Selectons songs from Max-Extreme).