Dean,
If I'm remembering right, you wanted to grind up 1 or 2 acres of sod, right?
Maybe I'm a "weany", but I'd be inclined to rent and beat up someone elses equipment before I put my Cub up against the size of a project like that. Don't get me wrong, the Cub will probably do the job, but somethings going to give. These tractors are tough, but they do have their limitations. Maybe if you broke the sod with a rental, then finished it with the tiller. That way you don't punish your equipment which, given the size of the project, IMHO is a David and Goliath scenario.
You know, the other thing you could do is host a mini-plow day and have a few guys help bust up the sod. Your cost: steak dinner to all and a port-a-poty; cheaper than the rental and good times. . .
Don't forget to "round up" the grass and let stand for a few weeks before plowing. It should help reduce the toughness of the sod.