Hi Simon. I only allowed the HAM subtype of RTTY in PocketDigi mostly because of my time lack to port everything. The other reason is to keep the UI simple, which is probably the reason of your question. I asked the same question about used submodes as you couple of months ago here at this list.
The only requests I got are from the yachters for allowing reception of DWD (Deutche Wetterdienst) broadcasts. http://www.dwd.de/de/wir/Geschaeftsfelder/Seeschifffahrt/Sendeplaene/broadcast_rtty_1prog.pdf http://www.dwd.de/de/wir/Geschaeftsfelder/Seeschifffahrt/Sendeplaene/broadcast_rtty_2prog.pdf The others are perfectly content with the just one submode. Hope it helps. 73, Vojtech OK1IAK