Large altitude errors etc., flying a 747-400 on AP/SITL<>X-Plane

Hello. When I try to fly a 747-400 on X-Plane using the waypoints and parameter files I copied from with MissionPlanner 1.3.68 and AP/SITL 4.0.0 Stable (or 3.9.8), I see the following issues: (1) the altitude varies in the range 290-635 m whereas the max. for any waypoint is 400 m (2) The flaps are fully deployed from start to finish, unlike in the video posted by @tridge, the inspiration behind my wanting to reproduce it. (3) Finally, it all my attempts the plane never landed on the runway!

When I load the params in MissionPlanner, one of the warnings I see is about 58 parameters that are missing. Do I need an updated param set for the newer versions of AP/SITL? Has anyone tried to reproduce the 747 flight lately? I run MissionPlanner, AP/SITL and X-Plane on an i5-6600K 3.50 GHz PC with 16GB of memory. Thanks for any suggestions.