I have downloaded the AN225.zip file from Fly Away Simulation and installed it with no problem. I am also using the default 747 panel as well. The problem I am having is that when locked to the glide slope and following it down with the AP and APPR enabled and the aircraft at 190 MPH with the flaps at 15 degrees, the aircraft porpoises plus or minus about 75 feet continuously rather than a smooth approach to the runway. It doesn't seem to make any difference what speed or flap setting I use it will still porpoise. Has anyone else run into this? Perhaps I am flying it wrong as there are no instructions on how to fly this behemoth. The only way to correct the problem is to disengage the APPR and AP and bring it down manually to stop the porpoising.
I have no idea how old the AN225 here at Flyaway is. I'd suggest you head over to www.flightsim.com and type AN225 into the "text" search bar. You'll find some models with updated flight dynamics.