I believe that’s the truth with the slim battery. The alternative is to find and buy a phat battery and pandora that instead. There are guides on how to do it on youtube.
Also with the load times issue. If your game is in .cso format and is compressed, it will instigate slower load times. Uncompressing or leaving the image in ISO format would allow for the fastest load times only limited by your memory card. In my experience if you’re using any Sony/SanDisk High Speed MagicGate memory card you should be optimizing the load times and the rest is really the fault of the game itself, though the read speeds on the larger memory sticks seem to be slower than the smaller ones. From what I’ve gathered the 4gb and higher sticks can reach around 15mb/s read speeds whereas the 2gb and lower memory sticks guarantee a minimum of 15mb/s and can reach upwards of 80mb/s though I can’t really confirm the legitimacy of that information.
I get a perfect game with slight slowdowns that are really unnoticeable in the end with Final Fantasy Crisis Core on a Sony pro duo while running 3.90M33-2, but God of War even uncompressed gets really slow. Though I’ve played enough GoW on the PS2 to last me a life time anyways.