Advantages of using temporary hack is that the device warranty is not violated and even if something goes wrong, there is no fear of bricking the device.
Developer qwikrazor87 at around the same time also released this PSP custom firmware. PRO-C f3 for 6.61, CIPL flasher left out intentionally since I don't know anything about it, I just used the keys/offsets for 6.60 (which won't work obviously).
Edit: For devs interested, only offsets I had to update were in
Using the PSPUsing Your Computer Using a UMDInstalling Custom Firmware Community Q&A Your PSP firmware controls your system settings, and new versions get released to add features and fix errors and security problems.
There are several ways that you can update the firmware on your PSP.
If you want to use homebrew software on your PSP, you can install custom firmware.
For those of you who are new to the concept of hacked PSPs, custom firmware might not sound so familiar. Homebrew is software developed by the user community.
There are two major variants of custom firmware (CFW) that are currently supported: PRO CFW and neuron's Minimal Edition (ME) CFW.
Choose the one that you prefer; though in truth, they are almost identical.
In this guide, we strongly recommend using Temporary CFW (LCFW).