AETR Initial Channel order for PIXHAWK

[Delucs]

Hi,
I do not know if this is the correct board, but hopefully.
I want to use a Pixhawk with my Taranis running OpenTX 2.0.
Pixhawk requires AETR as initial channel setup, but in order to make it work correctly, I have to set the Taranis (through Companion) to R(-E)TA to have correct behaviour of the sticks (Taranis being a mode 2).
I even set the Comapanion to default AETR for new models, but same problem.
I understand that I can associate a "function" A E T or R to a channel, but are ch. 1-4 always associated to the sticks and does that change from mode 1 to mode 2? (sorry, might be a dumb question)
A second less important problem is, that Companion does not see all my sounds? Are they not recognized when wrong sampling or is there a limitation to the number of sounds? (I know that names cannot be longer than 8 characters)
BTW I upgraded companion and OpenTX from a previous version.
thx
Luc