Something to remember is that you should really have some ballast on the back if you are doing a lot of loader work. Filling the rears or adding wheel weights will certainly provide counter weight for the loader, but the fulcrum is your front axle, and that's not good for it. And now you have the loader and whatever it's lifting on the one side, and the rest of the tractor AND the filled tires on the other.
Your actually going to be harder on your tractor if you fill the tires and do any significant loader work without using rear ballast. I have filled rear tires, and wouldn't have it any other way, but it's for stability and traction.
Adding ballast behind your rear axle will help to unload the front axle. I would at least get the ballast box, and load it with some weight.