the newest devhook supports up to 3.10 firmware so you might wanna try that.
i would really recommend custom firmware to you as the main benefits are running games directly from game menu in psp xmb. (this means there is no need for devhook so you can save some memory stick space).
also, you are able to customise your psp with custom icons,xmb wave etc.
do consider upgrading to custom firmware.
have a nice day.