No Headtracking with Pimax 4K Extended Mode

Hi Ralf, first of all, you are making a really great job with Vorpx, now with the last update that Vorpx support extended mode for generic HMD, now to the point ; I like to play with Pimax 4K in extended mode, because I get better resolution (2K) than Steam Vr but I had not headtracking at all, Is there any solutions or cofig that I am missing out ?? Thanks and keep the good job.