If you've run an OB tunnel and haven't flipped it then you haven't been driving it fast enough!
A good running tunnel is on the edge of flipping. My first 7.5 OB tunnel was an Aerotech, really heavy but a sweet handling boat. I took it to a nearby pond when the wind was really kicking up. I didn't think that I would flip that barge but I skyed it well over my head! I miss that boat.