Here's what I did in preparation to flash custom ROMs on my Xperia Z:
1) Root phone with towelroot
2) Backup TA partitions
3) Unlock bootloader (yes I have an unlockable bootloader)
4) Extract boot.img from custom rom and flash it
4) is where it fails. After I fastboot flash boot boot.img, the phone goes into a bootloop (pressing volume up when the purple led lights up does nothing). I've tried a number of custom ROMs with no luck (always starting from a fresh stock firmware).
Can someone please, please help me out here? I've spent the whole day trying to get it to work... :/