Converting 6550 camera to 6600 firmware
I think it is possible to update the 6550 camera firmware to the 6600 firmware.

What you have recited above, is the common procedure for upgrading or downgrading the firmware between like cams. The one thing that is not necessary is the 6600 to use as pv2 code. I have personally used unlocked blue's firmware on red's as pv2 or several others. The only real purpose of the pv2 code is to place a temporary copy of an unlocked firmware into memory. Once it is in place you upload the correct and permanent firmware to the cam.

I bet you asked for firmware huh? Whoops