You'll probably be ok, but as mentioned, you'll definitely know it's there. You may think that 600 lbs of gear in the TT is enough, but don't forget that water weighs a heck of a lot. Unless you plan to travel with all your tanks completely empty, you have to factor in water weight as well as the weight of your stuff. (And trust me, your stuff will weigh more than you think it does. Our last TT we had a small cargo capacity, and had to be careful what we carried. Nevertheless, we probably exceeded those limits a time or two.)