For most all situations weight is your friend as it helps eliminate the spinning of tires which in most instances is the contributing factor to getting you stuck. Weight also allows you to pull more load by increasing the traction and makes the tractor a bit more stable on inclines.. 4WD tractors require a slight slip between the front and rear tires, so adding any additional weight to the front end, could also cause additional stress on they front differential.
Most SCUT / CUT manufacturers dont recommend loading front tires due to the extra wear on the steering joints also. Most of the time, you dont need any additional weight on the front especially if you have a FEL. IF you need weight on the front because you are carrying a heavily loaded rear implement, just add some suitcase weights or build your own to hang on the front of the tractor.