Fluid in the wheel is better than weights on the outside when it comes to wear and tear on the rear end.
Think about it....
The fluid weight will not affect the rear end at all as it will be in the tire and not hanging on the tractor and will be more effective when it comes to traction.
That's 310# plus your butt plus what ever the ass half of the cub weighs, should do a great job with any implement you care to hang on the front.
I have 430 lbs of weight in the box of the 149 loader Cub plus fluid in the wheels.