Actually, the ultimate is to have the tailgate down and have the OEM bed extender installed in the back. Slide two 8 foot pieces of 2 inch diameter piping into the upper centre opening of the bed extender and tie them securely to the bars on either side of the centre opening of the bed extender. Plug up the ends of the pipes and tie a red flag to the pipes (both of them). I guarantee that you will gain a minimum of 0.005 miles per gallon with this setup. Remember to have the tie down belts on the bed extender snapped down onto the tailgate or you will get an annoying clanging sound. The same sound that forced one of our former members to take their entire rear seats apart only to find out it was the tie down belts on the bed extender when installed in the front of the bed position and the rear sliding window open and the windows up front open.
It's all about aerodynamics. The unibody design of the Ridgeline is so sophisticated that all previous findings and experiences with conventional trucks have gone out the window.
My findings are the result of hundreds of hours of highway driving with carefully placed pressure sensors around the Ridgeline. These sensors were hooked up to a laptop and using software that I personally developed, I get results that are as accurate as those derived from wind tunnels at testing facilities. I have applied for patents in both the US of A and Canada for my software and setup. I will keep you posted with other findings.
I am also working on a device that will pre-atomize fuel to improve gas mileage by 45%. I have perfected it, but have been forced to stop because the oil companies have slapped a lawsuit on me. Before that, the oil companies got the government of Canada to stop my efforts by claiming that my experiments were too much of a danger for the facilities I was working out of.
Edit: forgot to mention that the two pieces of pipe must be kept parallel with each other at all times. If they are out by even two centimeters, the setup does not work.