If you are planning using your truck off-road in snow you boughtthe wrong truck(2wd vrs 4wd)
If you are planning using your truck on plowed city streets, I don't think you need anything but good all season tires and prudent driving technique.
I understand that weight over the rear wheels increases traction but it also increases overall vehicle weight.
In off-road (low -traction) use I wanted the lightest vehicle possible, low weight means lower power required to move it, lower power required ment I could move in lower traction situation.
I think the best use of carrying the sandbags is that you can empty them on the ground, increasing the traction
Carrying a old piece of carpet (say 4x8) can be put down and it will allow you to move the vehicle onto a better surface (helped me more than ever carrying sandbags)
BMW's are some of the worst performing vehicles in low traction conditions,many people (including me carried 200lbs of sand in tubes in the trunk)I cant say it helped.
I have a 2004 F-150 and don't plan on carrying any weight
Think of the gas mpg you will loose carrying the extra weight,and for what benifit
People post here all the time in much distress over a 2mpg decline.