I will give this a try...first of all, you'll need to download customizer version 1.4 as 1.5 is being tweaked because of some unique USB problem.
When you download firmware 1.2, drag it into the contents of the firmware folder in the customizer. Go through the customization executable (choose the replace firmware option and select 1.2) and when you are done, you will be prompted to load the contents of the SD card folder onto your card. Do not load the folder, rather open the folder and add the contents of the folder to your card. Once you've done this, turn on your reader and then load in the SD card.
You'll see the Sony split circle rotating, then a menu will appear. Press number 4. Once this routine is done and the menu reappears, press number 6. Let the unit process the change. When the menu reappears, press number 5, then when this is done, press number 6.
After the unit reboots, you will be done.