Yup. load up the other front or get rid of the fill. You want all tires balanced.
Loading the fronts is fine as long as they are balanced. Don't overfill - you want the weight low (at or below axle level). Remeber that liquids will splash inside the tires and can actually raise your center of gravity. Fill the remainder with air to the same pressure as you normally would. If you don't need air, you probably have too much fill in there.
Foam filled is best, but most expensive. No more flats is an added bonus. Do this when your tires are new - it isn't worth it on older tires.