I tried to customize a reader with the uk firmware. result: hanging on the startup screen.
problem with unbricking: if you follow the instructions unbricking with the us firmware won't work, as it will show that the firmware 1.1... you try to flash is older then the uk 1.2....
solution: edit the file as described in the unbricking tutorial, but: chancge the seceond numer instead of the last: instead of 11something make it 12... or 14... something.
this will enable the flashing as the updater will think now you have a newer version.
when the prs works again, you need to change the verion number to 1.1 again to be able to update it in the future. this is simple: just put in the sdcard you tried to cutomize from, and choose the option to change to the firmware update mode.
on your computer restore the original version number, or simply use the unchanged update. the reader will show version 000000 so you can flash the original us firmware with the number 1.1.
do the whole customization process agian, but this time choose the us version, not the uk - and you see: it works
why i wrote it? well, i could not find anything that would describe the situation i was in and save me some time, so i hope if it happens to someone too, he'll see how to get out