I do not have a PX5 model, nor have I gone through the process. However, there's a bunch of people who have in this thread. The search function at the top of this page that allows you to select "this thread" to narrow down the replies to search terms if you want to read through people's experiences/etc.
That said, my understanding is that upgrading Android versions is a bit more involved than OTA updates. It can be done with the factory method, or using Hal9k_'s mod installer (you may have to buy it).
Here is a link to his post on upgrading
Here is a link to his mod installer (he recommends using it instead, it's in his signature)
Best of luck!