Center of gravity has to be the difference felt between the two campers on the same truck.Arctic Fox CG's are all over the board from the AF-811 to the 992 where Lance's are all pretty close to the same except for the 850.
AF-992 "46"COG" Lance-1062 "48 COG"
AF-992 "54.5 COG" Lance-995 "45 COG"
AF-811 "39" Lance-975 "49 COG"
AF-865 Non slide"?" Lance-850 Non slide "39 COG"
The difference felt between the AF-811 and the Northern lite 990 on the same Dodge 3500 DRW must have been the COG difference.There is 10" difference between the Lance 975 and the AF-811 in Center of gravity.
Granted I do not know the COG of the Northland and could not find it but I would be willing to bet it is much closer to the Lance than the AF,,,