Thanks for all the info. Although Taranis works with it and I cannot see any obvious delay it seems a pity to go to a much slower frame rate in this day and age. Though I have a feeling that the famous futaba 9zap was about 30ish frames/second in 9channel pcm mode and nobody complained about that!

The Taranis shows the frame length that it chooses as a safe rate when you select the number of channels. You can then change the frame length to whatever you want and I can turn it down to 25 or even 20ms which equate to roughly 40 or 50 frames per second respectively. But I do not want to do that as I don't know how it will behave if the sum of all the channel pulses exceeds the set length. I will pose the questio in the opentx forum and see if one of the developers knows the answer.