You should be able to handle a 5' just fine. You may not be able to fill it with dirt and go up steep inclines with it, but for normal applications it should well. You'll be best off if you're tractor's a 4wd.
You will also be able to pull a lot more dry dirt/stone than damp. Using a box blade at any angle in damp conditions will result in taking a deep bite and too much weight for a SCUT or CUT.