Thanks for the response, I'm trying to downgrade from 4.0 to 3.55 so that I can apply a custom firmware. I've check using the original firmware check and its base firmware is 2.41. So from what I've read I should be able to downgrade to 3.55.
The guide i've been using says that I need to reboot my PS3 with the hermes v4 HEX flashed to my AT90USB162, which would set the PS3 in service mode so that I can apply OFW 3.41, which I can then upgrade to 3.55 and apply CFW as require.
Could you please let me know if i'm going about this the wrong way, and any pointer would be very helpful.