Sounds like you've already done the deed.
How big is the ballast box, dimensions?
For my
B3030, the ballast box is 15x15x30 inches. I wanted to at least compensate for the snowblower once spring came along, with the option to add weight as needed.
I went around to 3 tire shops and scammed the used wheel weights removed from wheels. The lead is more dense then concrete, so I figured adding the wheels weights to the 'mix' would provide more weight in less volume.
I planned to fill the ballast box with weights and concrete, then reminded myself to check the maximum load for the lower links on the 3pth. Turns out the maximum is 800 lbs. I'd actually planned to put in weights/concrete that would have exceeded that. As a result, I re-thought my plan. As the saying goes, if you haven't got a plan - you can't screw it up.
Anyway, I welded a received hitch to the bottom of the box, added one 60lb bag of redi-mix, distributed the wheel weights, and then topped up the whole affair with more concrete. The box and receiver hitch alone weighed in at 80lbs. Add the concrete and wheel weights - it topped out at 550 lbs which I think is appropriate for my needs, PLUS there's room to add steel (weights) as needed, rather then topping up with concrete. (I actually weighed the wheel weights in 3 - 5 gallon buckets on the scales that I avoid in the bathroom).
As usual I've elaborated at length, but then again, that's my thing...
