I've got a tc40 myself and it takes practice, but it can be done. The key to maintaining a flat and constant depth is to keep the tractor on flat ground. I know that sounds goofy, but if you create a wave you really need to take it out right away. If you spin spin your wheels and create holes, you need to fill them in right away. Every ground lump, bump or dip is magnified when you drive over them with your tractor. This will be time consuming, but the finished product will be much better for your effort. The other recommendation I'd make is don't try to cut to final grade as you go. I'd rough it out to within a couple of inches and then take it down to the final grade. By the time you rough it out you'll have gotten some practice and your final cut will luck like a pro did it /forums/images/graemlins/cool.gif
I wish I had something like this to work on this weekend. I've got all my tractor projects caught up and now the only projects left require a shovel and a rake /forums/images/graemlins/frown.gif