TN-Hen B: Released by Total_Noob
A new revision of Total_Noob's Hen for the firmware 6.20 has been released. Thought I'd put it here for those that didn't know yet. This new revision allows downgrading (even for the unhackable motherboards ie 2000/3000/Go)
Download link for 6.20 TN-B below.
Below is the full changelog, comments in italics are by wololo (developer of Wagic and Half-Byte Loader)
* -Fixed homebrew execution crash on some PSPs (thanks to HacKmaN for debugging)
* -Added 4g model support (this will fix issues for most psp3000 users)
* -Resolved some important NIDs (this means more plugin and kernel homebrew compatibility)
* Added FAKE INDEX.DAT to TN VSH Menu.
* Dump whatever FW with psardumper.
* Copy /F0/vsh/etc/version.txt to /seplugins/version.txt.
* Enable the option and restart VSH, now your PSP version is faked. -> To downgrade just dump a lower FW. (I do not recommend to downgrade if you have a unhackable motherboard until it is proven to work. Downgrading is most likely useless, and on some models will give you a brick)
Downgrading has been confirmed on the 3000 model by many users, I myself haven't downgraded yet as I couldn't care less for lower firmwares, but if you're worried about bricking your psp, then don't downgrade, you have been warned.