UPDATE - After 10,000 miles at highway speeds, the kayak rack has had no problems. I did just replace the bottom boards because they warped a little from being stored outside, but it was a simple job.
I finally built a kayak rack, and it's been an unqualified success. I've had a lot of people ask how I did it - I initially built 2 racks, one for each end of the kayaks as shown in the photo above.
But I found that instead of 15 MPG towing the camper, we got 9 MPG when we had the kayaks over the cab of the truck.
We even carry a Hobie Tandem Outfitter Kayak this way and still get great gas mileage.
