Hi Guys
I had this issue as well, I managed to resolve it by deleting the C:\Users\USERNAME\AppData\Roaming\Lockheed Martin\Prepar3D v3 folder.
Note, you may want to back up the dll.xml first.
I think the proper questions is 1.) Does the real DC6 have wing flex to a discernable degree and 2.) if the answer is yes, has PMDG modelled it (I bet that if 1 = True then 2 = True)
I ran that same flightplan in PFPX but said no weather and got this:
FUEL CORR ENDUR
TRIP 113144 ........ 13:15
CONT 5% 5657 ........ 00:51
ALTN 3079 ........ 00:22
FINAL RESV 3312 ........ 00:30
HOLD 1678 ........ 00:15
MIN T/O 126870 ........ 15:13
EXTRA 0 ........ 00:00
TAXI 340 ........ 00:10
RELEASE 127210 ........ 15:23
then same but with live weather and got:
TRIP 108755 ........ 12:16
CONT 5% 5438 ........ 00:48
ALTN 3090 ........ 00:22
FINAL RESV 3370 ........ 00:30
HOLD 1706 ........ 00:15
MIN T/O 122359 ........ 14:11
EXTRA 0 ........ 00:00
TAXI 340 ........ 00:10
RELEASE 122699 ........ 14:21