I have ridden All my sportbikes on every 4wheeler/atv trail that they had the ground clearance for.
Alot of times they were the shortcut home.
I have pics on my laptop that I've posted here before, I can add them again later.
I've also been 130-140mph on a gravel road.
The bike floats a little at high speed on gravel, but with no sudden moves, handles fine...just have plenty of extra room to slow down. Being able to drift a dirtbike is the same as following the curves in the road on gravel, if the curves are sharp enough.
As for traction in the dirt, it obviously isn't much, but anyone who has dirtbike experience(which you do) will have no issues at.
Grip it and rip! As long as there's ground clearance and enough throttle, slick sport tires will go anywhere.