You really want weight behind the rear axle to make that the pivot point, any weight on the rear axle (weights, or water ballast) will work but you're still using the front axle as a pivot with far more weight on than its meant to have, hence why loader tractor front axles wear faster than non loader ones. I find with our mf 5610 that with an ibc on the forks it doesn't want to steer well unless I put the rear weight on. And it has rear wheel weights already.
The pivot point will allways stay on the front axle by adding more weight further out of the rear all you are doing is counterbalancing the weight on the front I spent years with for end loaders and weights from a David brown 780 and brown loader with a block cutter to a David brown 996 with the same block cutter then John Deere 1640 and tanco loader then on to a shear grab with the same loader but we reenforced all the beams and fitted rams of a larger loader then finally a John Deere 3600 with John Deere loader both the 1640 and 3600 were 4 wheel drive