If you have huge myopa like me you can remove the foam it helps to get a clearer view.
Using a cardboard in order to adjust your vision would not be my decision. We surely can mod a little bit the pimax in order to increase the distance between the lenses and the screen.
I think the lenses are not bad, that's the ipd and the focus which are not right for certain people.
By the way it's more easy to set the right ipd when you have a good focus.
I hope that they will release soon a new firmware with ipd ingame setting.