Here's a chart for how much fluid (US gal) can be put in tires, and how much weight would be added if you use Rim guard.
Someone might want to make this a sticky some where.
>Rim Guard Hydro-Flation Tables for Agricultural Tires | Drive Wheel Tires | Terra Tires | Light Construction Tires
Suit-case weights are good because they can be added, removed or moved, front to back quickly and easily.
Wheel weights or loaded (fluid filled tires), add weight right where the tire touches the ground, no extra load on the axles or wheel bearings.
Windshield washer fluid is easy to get and cheap, a little lighter than water.
Plumbing or RV anti freeze costs a little more but less hazardous, weighs about the same as WWF.
Rim Guard probably the most expensive but heavier than the above and not toxic at all.
Calcium is cheapest and heaviest (lbs per gal), but will rust the rims and is toxic.
What I learned back in jan.
Fill the back tires with what ever fluid you want, then add extra weight if needed using wheel weights, suitcase weights, weight box, what ever you have.