I hesitate to post this but I think it is worth discussion.
I have two trucks. They are as follows:
1 One is a '96 Dodge 2500 Ext Cab DSL long bed
2 The second is a '04 Dodge 3500 Quad Cab DSL 4x4 DRW long bed
I have used each truck to carry the same 4000 lb TC and I have weighed each truck with and without the TC several times. The TC sits in the same position in the bed of either truck. I have placed the TC on a pipe and balanced it to locate the center of gravity, which is 4" in front of my rear axle.
I do understand the rear springs will have an impact on this, but I was always of the thought the following to be true:
1 When you loaded the TC, if the front of the truck dropped more than the rear, the COG was in front of the rear axle.
2 When you loaded the TC, if the rear of the truck dropped more than the front, the COG was behind the rear axle.
3 When you loaded the TC, if the front and rear of the truck dropped the same amount, the COG was over the rear axle.
This is true on my '96 Dodge Ext Cab, it drops in the front and about wtp lbs of weight is added to the front axle.
It is not true on my '04 Dodge Quad Cab DRW 4x4. The front axle is lighter by about 60 lbs.It appears the wheelbase has a major effect.
Wayne