Here’s a neat trick: if you reconfigure the PN532’s RF front-end in the ACR122U for maximum Rx gain, you can extend its range considerably.
I made a small Python script to do just that. It runs on Linux. I don’t have Windows, sorry, but it should be easy to port if you desperately want to use it under Windows.
I also made a small udev rules file that calls the booster script automatically each time an ACR122U is connected, to go with it.
You can find the script and the udev rules file here:
And in the tradition of “video or it didn’t happen”, here’s a range test video 