While I have a Thule bar set and towers that fit my new vehicle (2014 Hyundai Santa Fe), the instructions indicate that the bars should be set ridiculously close together. So, I went with a single bar (roughly over the driver door) and a
(You need to Login or Register to view media files and links) (mine came already assembled but was more expensive) which mounts to a trailer hitch tongue. I modified the top t-bar to accept a metal handrail post that would insert into the end of the bar to add side "wings." This was then fastened to the t-bar by drilling multiple holes in the handrail post and a single set thru each end of the t-bar and finally held in place by
(You need to Login or Register to view media files and links). I use the wire loops on the pins as anchor points for tie-out (ratchet) lines down to the bumper to add lateral stability. Before the tie-out lines attach, the top of the "T" will swivel, which makes loading a single canoe much easier.
Now the downside of this arrangement is that it blocks a pick-up tailgate or a lift-gate on a hatchback, so you will probably want to load your "back end" before placing the canoe(s) on top.
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Follow-up: The "wings" (one each side) were crafted from these
(You need to Login or Register to view media files and links) sections, cut off to an appropriate length ... holes drilled about every 4 inches so the remaining length could be adjusted and locked into place with the pins. I also threaded an eye-bolt through the holes already present near the top as a tied-down point near the ends of the assembly. I placed an adhesive rubber strip on the "top" of each of the sections and reflective tape to the rear-facing edges of many of the parts.