Foam filling the fronts can add a little weight. Each tire ends up about 60 pounds. It helped me a lot with steering control while using a rear snowblower.
Exactly, I assumed he needed the extra weight because the loader would be off.
With the loader on you can add at quite a bit of weight-unless of course you want to use the loader. Maybe manufacture a mod for the top of the loader that will allow you to mount the weights and use the loader at the same time?
With the fel and b/h on it, it's only too light in the front, if your doing something it was not designed to do, like pick up a lot of weight with the b/h extended.
In which case, you can fill the front bucket with gravel, etc., first.
As they are 10 inch wheels you could look around for some old garden tractor wheel weigths. Then you could bolt them on the front wheels. If memory serves they weigh about 30 pounds each. Another option is to make a bracket and use free weights as needed.