It would be counter productive to have front weights _and_ a loader on the tractor at the same time. The front end has plenty of weight on it with the loader, or even just the loader brackets add a lot without the loader.
If you tend to use the tractor without the loader a lot (that is rare, despite initial intentions, most folk don't remove the loader very often...) you might need the weights but really I'd throw them off and probably never touch them again unless you take the loader off & you have something heavy on the 3pt.
Perhaps you could make a nice bracket for your 3pt and hang them on the rear end to help with the loader.
--->Paul