What makes the headset prone to distortion is the wide FOV and the limits of the dual element fresnels they are using. A normal Aspherical or Fresnel lens tops out at 130 degrees before introducing weird artifacts.
When the HMD is on “normal” FOV (about 140-150 degrees) people by and large have reported much less distortion, but this high field of view of 170 degrees together with the canted displays push these optics to their known limit.
Pimax could actually eliminate almost all of the distortion on these optics if they rendered four cameras (2 view ports per eye,) but that would require developer specific support, would be more computationally expensive, and would also lose the wide comparability with all the software (Oculus and Vive) that they can use.
I do suggest that if people want better software on Pimax, talk to the developers who make your favorite titles, and mention to them quadport rendering that StarVR uses, variable rate shading, etc. for them to employ in Pimax specific versions of their games.
Without changing the lenses themselves, or without devs making specific versions of the software, not much can be done.