... Spectrum advises not to use servo reverser in their 2.4GHz radios (possibly because of signal integrity issues with digital servos).
I have Futaba FASST and use analog servos for the Hawk elevators ... Futaba even makes their own servo reverser :
... no known issues with FASST.
Been flying servo reversers for ten years in almost every other edf jet ...
But then, in case of lingering doubts about electronic mysteries, reverse the position of one of the two elevator servos