If you want to see if you need more weight on the rear, just put it in 2 WD and try backing up a slight incline with your loaded FEL. If the tires spin rather than grip, then you need additional weight on the rear. It may not look like it is light on the rear, but you can see rather quickly how much stress is on the Front wheel drive when you do this.
Recently my front wheel drive went out and I drained all the water from my tires in order to haul it to the shop without overloading my trailer.
With the FEL on, it wouldn't climb up the ramps when the trailer was on level ground, just spun the tires. I had to position the trailer at the bottom of a steep hill so the ramps were almost level in order to get it on the trailer.
With no weights, no ballast, no 4 WD and a FEL on a tractor, they don't have a lot of traction in the rear.