The sand bags would sure be a cheap and easy thing to try. If they worked to suit you, keep them. If you feel you need more weight, keep your eye out for some scrap cast or someones unused tractor front weights. You can always use the sand elsewhere.
One thing that is handy is having a place on the tractor to store a chain. A 16-20' 5/16 gr70 chain is invaluable to have with you all the time (especially if you weld 2 grab hooks on your loader bucket as I suggested). Keep that in mind with your weight box and think about incorporating a chain box or rack back there too.
