TheBuzzer has just released the final version for his DevHook mod which is GUI DEVHOOK Launcher v3.3, so check out the screenshot and download the file for your PSP. In the meantime, TheBuzzer has included the following installation directions in his readme file:

devhook FW2.71 with MemoryStick file root directry.
flash access is redirect to this directry.

You should be copy all files of flash0/flash1 and reboot.bin.
replace flash0/kd/*.txt with plain modded config files.

FW installer can not make reboot.bin.
You yourself must copy it.

flash1/registry/*.* copies from other FW ver.
because FW2.71 with devhook can't initialize registry files.