2.0 GAMEBOOT on a 1.5 PSP! Here's how.
Once you have a firmware dump of the 2.0 eboot look for the opening_plugin.rco. Use UMD Emulator's Flash emulation and put the file in m0:\F0\vsh\resource\ and voila. I am going to try PSP Personalize to flash it. Wish me luck.
PS. This has probably been discovered before but I had asked for help a long time and had to figure it out myself.
BTW: MAKE SURE THAT THE ROOT OF YOUR MEMORY STICK IS CLEAN OF ANY FILES BESIDES THE ONE IN QUESTION. You can brick your PSP.