I am planning to build a ballast box for my BX2200.
Since the FEL can only lift 460lbs. I cannot imagine the box needing more than 100 to 200lbs.
Does this sound right?
The heavier the counterweight the less stress on the steering\front end. The tractor will spec out what the 3PTH capacity is. I would not go less than 250 lbs. I use 200 lbs on my 12hp B4200 (1,000 lb tractor) for a loader that lifts 400 lbs. Not having power steering, you can feel the difference the counter weight makes. I use about 500 lbs on my B3200.
I use 50# suitcase weights either front or rear depending on situation. Neat part is the variability to go from 50-500#(I have 10 of them). once you load the tires you are stuck with that weight. A water tank could do the variability but the sloshing around would scare me.
I love the counterweight that the BH or back blade or rake give me. All are well over 200# and their CG is probably further aft than your ballast box will be. I would size to be compact and ability to load it to about 400lb... maybe a little overkill. I haven't done the math on overhang distance vs. load but if I ever made a ballast box it would be for tight situations when I could not use leave an implement on my 3pt or the BH.