Late-2011 MBP (A1286) Serial Number Locations

Hi, I've been working on a Late-2011 15" MacBook Pro for quite some time, trying to figure out how to change the serial. I've managed to gain some success, but am still facing an issue. Here's what I've done so far: I removed the EPROM from the MacBook's logic board, and created a dump using an EPROM programmer. I then opened that dump in a Hex editor, located the original serial number, and replaced it with a desired one (from a MacBook of the exact same model and specs), making sure to keep it in the same offsets as the original (and not add any blank bytes/spaces to the file, obviously). I did this successfully, and wrote it back to the ROM, then soldered it back on the logic board. Machine booted just fine, however the serial number (and related specs) would no longer display in Apple Hardware Test. I also ran Blank Board Serializer, which also detected the serial as blank, but when using it to try to write the serial, it just errors out and doesn't do anything. The modified serial shows up just fine in OS X, however (in Single User Mode, I can't fully boot OS X as the GPU on this board is bad). I then tried a few other serials with the same result. After those failures, I decided to type my original serial back in my dump, flash again, and sure enough, it worked exactly as it did before I changed the serial at all. I then tried cleaning the ME region of my dump with the modified serial, but that didn't change the results at all. I'm stumped at this point. Is the serial stored in some other chip on the board, causing it to come up blank in AHT and Blank Board Serializer when the one in the SPI-ROM is compared to it? Any help would be greatly appreciated. For reference, this is a Late-2011 MacBook Pro 15", model A1286, with a 2.5 GHz Intel Core i7 CPU. EMC number is 2563. The clean dump, with my original serial number (C02HD0QRDW47) is attached, as well as some pictures of the issues I'm having.

Let's take a closer look at the EFI dump. Perhaps there's a board ID as well as a board serial which needs changing?