All of you are making some good points, thanks! I'm attaching a picture of what I guessed is 150lbs of sand. As for the weight of the loader, I read that number right off the spec sheet (I did round it up, the actual value is a little under 1500lbs). I was surprised too! The Woods 1012 is under 800lbs, so the M246 is much heavier than other loaders that are available for the TC29. I even called Bush Hog and asked them why it's so heavy and they said that 450lbs of that weight is the mounting kit to strengthen the tractor frame, so even when the loader is detached, I've got an extra 450lbs on the tractor.
What you folks are saying about rear ballast makes sense and I don't dispute that. I realize that I’m going to need rear ballast, but was surprised how much and that I would need it for only a couple hundred pounds of weight in the loader bucket. I'm disappointed that I've got more weight to counterbalance than I need. If I had a lighter loader to start with, I could get by with less rear weight and still be safe and not tear up the ground so much.
I'll try to do some more precise tests. I was facing downhill on a slight slope with the sand, so on level ground it might not have been so bad. I haven't tried standing in the bucket. I weight 180lbs, so I'll see what that does and see if I can bring the rear end up. I've also got some sandbags that I know the weight of, so I'll experiment with them. Don't worry, before I try to lift anything heavy, I'll attach the finish mower or tiller, which weigh close to 700lbs.