Full disclosure, I am currently running Elevate TS rails clamped on top of the standard rails with a Bison tri-fold. It works, but a cover that integrates both in the same extrusion is the right way of doing this.
Thanks!
Ordered the extrusions at the proper lenght with hardware and just assembled. No cutting required. I used rectangular 15 series (1.5 inches x 3 inches) but it is overkill as I was comtemplating putting a roof top tent on the bars.
If I had to do it again for bikes only, I'd go to a...
Not sure if that can help but I have the Elevate t-slot tracks and I made a rack out of aluminum extrusions to hold 4 bikes. Used the hitch for the cooler and other stuff.
MPG not afffected. Heavy face winds made MPG much worst than any cargo on that particular trip.