rewriting HID device usage strings?

So here my Dilemma, I've been trying to get my Saitek x45 joystick and throttle to work properly with the flight sim game F/A 18 OIF. but I'm still not getting all the buttons to map right in game. So I would like to overwrite the button map in game to reflect all the buttons on the X45. I've tried several external programs such as ControllerMate, USB overdrive. now these come close but not quite I still get some button mapping problems. So here my question, Is there someone out there who's willing to guide me through process of writing my own button usage strings for the x45 so that it'll map right in game.