Here's one not to try. Here's the flight plan:
[flightplan]
title=NZNV to AAAS
description=NZNV, AAAS
type=VFR
routetype=0
cruising_altitude=13000
departure_id=NZNV, S46* 25.13', E168* 18.30', +000005.00
departure_position=4
destination_id=AAAS, S78* 0.37', E24* 47.68', +011283.07
departure_name=Invercargill
destination_name=Amundsen-Scott Station
waypoint.0=NZNV, A, S46* 25.13', E168* 18.30', +000005.00,
waypoint.1=AAMQ, A, S54* 31.00', E158* 56.87', +000002.25,
waypoint.2=AADU, A, S66* 41.80', E139* 57.32', +000005.45,
waypoint.3=AAVK, A, S78* 27.85', E106* 51.95', +011336.62,
waypoint.4=AADV, A, S68* 35.00', E78* 15.00', +000002.11,
waypoint.5=AASY, A, S69* 1.40', E39* 39.17', +000003.19,
waypoint.6=AAAS, A, S78* 0.37', E24* 47.68', +011283.07,

If I'm not mistaken, in the Cessna, the GPS is tied to the magnetic heading indicator. If the heading on the GPS is 090, the heading indicator should read the same.  Here's the problem: Between waypoints 1 and 2: the compass heading went all messed up. I was eventually able to fly by heading only, not GPS.

The GPS showed a bearing of 084, but the only way I could track it was to fly a heading of 200, and make minor adjustments to stay on course. I think I flew over the magnetic South pole. any solutions?

Here's the link to the map of the flight:
http://simviation.com/yabbuploads/Magnetic_South_Pole.jpg

I do bring up the fps using shift Z. The heading on it matched the heading on the GPS course, but the heading indicator showed 200 degrees. I set this heading using the heading adjustment knob and was able to track the GPS course fairly well. At either waypoint 1 or 2 in the flight plan, the heading indicator matched the fps perfectly. I read somewhere that the geomagnetic south pole is off the coast of Antarctica. When I fly from South America to Antarctica, I do not get this deviation.