Put the 13599 SE image, called SE.13599.bin inside the loaders\5BL folder

You will need all the files below in the filesystems\13599-dev folder
Hex edit the first letter to a 'C' (to make 'CE' instead of 'SE')

Get these from a DEVKIT nand:
bootanim.xex
dashboard.xbx
xapi.xex
xlaunch.strings
xshell.xex
xstudio.xex

You will also need these from your RETAIL nand:
crl.bin
dae.bin
extended.bin (+ .meta)
secdata.bin (+ .meta)

CD.8453_falcon.bin is required for all phat xboxes using 8453.