Well, everything is on the forum shattered between threads, but basically some testers removed the lenses, measured distance between lens and panel, put the lenses above a newspaper at that same distance and marked the part that could be seen through a lens and then measured that. It's about half of the panel.
However @Heliosurge suggested that possibly errors were made. I can't verify this of course since I don't have the HMD myself. In theory errors could have been made. Also it could be that (at least) some HMD's that Pimax sent out were botched. It's confirmed that not all testers have the exact same hardware anyway.
Like Sweviver revealed, basically the Spanish tester group concluded, on basis of the specific hardware they have seen, that the lenses are sh*t and need to be redesigned. But the question here is if Pimax is even capable of making better lenses and if so, how much time this would take. This should be seen in relation to how people feel the lenses currently perform. If they can live with how the HMD currently performs, then it might be the best idea to just release it. I don't know man, these are difficult decisions. At this point people are not expecting a perfect HMD anymore, so maybe some/most will feel the current version is good enough and should be released. I had wished that Pimax would have planned more time for each backer in Berlin, so they would get an honest and good impression. Now I'm not so sure if 5 minutes in a controlled setup will do.