To anyone wondering, no you can't use 2.8x on devhook yet, why ?

1 - You need another compatible devhook version

2 - There is a new security in 2.8x reboot.bin that allready existed in 2.00+ IPLs, in 2.00+ the module possess a sha1 key area that is beeing generated by 2.00+ updaters before the modules are actually copied to flash0.
This key area is generated from idstorage data which is unique in every psp.
The 2.00+ IPLs check if the modules key area match the idstorage data.
If it didn't then it wouldn't let the module load. The reboot.bin didn't have this security, but 2.80+ reboot.bin now does, so technically you can only devhook a 2.80 firmware if you use the modules from your own nand dump. (which can only be achieved if you manage to dump the nand on 2.80 and extract lflash from it, at this time only people with a modchip can do this)
There are 2 ways to bypass this limitation, either we hack reboot.bin to load the modules regardless of the sha1 key area check results, either we manage to generate the sha1 key area on the modules.

The second solution is the best and can be achieved by performing a deep reverse into the 2.80 updater and reproducing its work.