the only other issues will be soil quality (clay content) and application.
A T-300 is pretty small WRT capacity to move volume. 2 of 'em isn't very impressive, either. I relent to the dirt guys here, but a job of the size you describe, IMO, may be better done with MUCH larger equipment. How are you being billed (if I may ask). I would be concerned for efficiency vs. cost. Are there any plans for larger equipment, scrapers or earth movers?