You have to look into a hardware flasher and soldering it in the ps3. Since the firmware is so high I take it that you have a ps3 slim. You can use the progskeet, e3 or the teensy to do this.
So do some looking into getting one of them first and then we can go from there. Also you could pay someone to do it for you. I do downgrades for people as well as some others. Take a look at my forsale area as there are pictures in there as well of progskeets hooked up to the ps3s if you want to see what it looks like. Thanks.