We did it a couple of weks ago in a 6.65mtr and 2.70 wide camper (so nowhere near as big as yours) and frankly although we didn't really have any problems I would never do it again, it is just not worth the risk. At times our wheels were only just on each side of the tarmac and one slip off and you are going to be stuck, and holding up a whole load of other users. The views aren't that great either, particularly as there is little chance for the driver to take his eyes off the road. So my answer is yes you will probably make it, but if you drop off the tarmac you are going to cause everybody a big problem.