In my installation I had a servo on each side of the fuselage. In order to keep the geometry correct, I had to reverse a servo. Futaba servos are not easy to reverse so I connected one to channel 2 and the other to channel six and inverted it(6). It is my understanding that to fit 1028 bits into the bandwidth restrictions on 72 it required two updates.So PCM required two updates. PPM did not need that and so its latency is 1/2 PCM.On 2.4 you have plenty of bandwidth.
I updated my 9C to XPS where all outputs are output simultaneously. Wheatronics may do the same. But you are still stuck with the latency of PPM