Temporary 3.50 Game workaround
Another user came up with this idea for another game, but I've just tried it with Fist of the North Star and can confirm it works. If there's an NTSC USA game you're trying to play and the PARAM.SFO patch doesn't work, then if you locate the EBOOT from a different territory (PAL, NTSC JAP) that only requires 3.42, the game will boot and install successfully. No problems with Fist of the North Star so far, but I figured I'd save some people time since I actually bought the game only to discover it didn't work.