Hi,
the 2015 sr5 has a roof rack that only extends 2/3 to the front of the roof. I want a simple, cheap, possibly DIY solution so I can mount either a full length set of bars or just some kind of custom mount to put crossbars on. I would then put the canoes on top of the crossbars and tie them down.

So for clarity, you want to be able to carry just one, or two canoes? I just have yakima 48 inch crossbars on the stock rails and have hauled a 16 footer long distances no problem. Two tie-downs over the hull and around the bars, and a bow and stern line attached to the front and read tow points.

A 58 inch crossbar is probably better, but the 48 does the job.

I've used the foam blocks many times without issue.

https://www.rei.com/product/883823/s...c:cse_PLA_GOOG

^ neat idea!

They make a similar product for kayaks too:

https://www.youtube.com/watch?v=_ThJeYV6xu8

here a 2nd manufacture's solution:

https://www.youtube.com/watch?v=H-ZO...8muqp-29nskyDA

Seems like one could buy the foam and straps and DYI a similar solution.

I have a similar need with my Yakima skybox. even with the yakima bars/ grabs, the best I can rig it, the rear hatch will still hit the skybox. Gobi, Drabbits and K9 make full length rack systems, but they are pricey.

Not really cheap but simply and rock solid - Thule crossbars. Have it for few years, worked for me on highways and offroad. Take 10 min to install/remove and holds canoe very secure:

I've used pool noodles cut down the middle and secured around parts of the gunwale for a long time without issue.

Exactly this. The 4Runner has really easy to access to tow points so its quick to tie down the bow and stern too. The canoe is really secure when does as above and won't be going anywhere.

My canoe is 18.5 ft and i was concerned that it will stick out too far on the back end. There are also times when we will have 2 canoes on the rack. I thought we would have to have a mounting point on the front of the roof as well to balance things out. I think i would use at least 72 inch crossbars, as I do not want the two canoes to rub against each other when being hauled.

Having bought my 4Runner specifically to carry long boats, I would like to add my 2 cents! For a sturdy canoe, a set of Yakima or Thule bars attached to the stock rack would be fine. It's ok to have the stern of your canoe sticking out the back, but most states require a road flag on it. And the bar spread distance would be fine for a solid stable carry. Thule makes Gunwale Brackets to hold the canoe in place. Little cushioned L shaped things that cradle the gunwales and prevent lateral movement. Like a couple people said though, it is imperative that the bow be tied down before you go down the road. Thule makes these little loops that go under the hood near the edge, with webbing loops to tie the canoe down left and right of the bow, to prevent it from going sideways on you. If you're only going once or twice a year, just use the foam blocks, above.

Scanny has shown the best easy way to support and tie down one canoe. I've hauled a canoe on stock roof rack crossbars before and that works the same way. Hauling two canoes sounds like they'd be too wide for the truck. Are you sure they fit on 72" wide rails? One cheap easy solution is to place two 2x4 boards flat of the width you need at the front and back of the roof side rails. They could be locked down in the rails with some hook hardware. I've tied the boards down with 1/8" line before. Then tie the canoes down at the front and back corners of the rack similar to how Scanny shows his tied to the Yakima bars and tie the canoe off front and back.

Yes, the canoe hangs over the back end a long ways. The canoe is placed to balance somewhere near the middle of the rack. I've driven with a canoe mounted the same way at freeway speeds with no problems. I worry more about the wind catching the canoe and turning it sideways at 70 mph. Tie it off well in front.

The only way I know of to load the canoe with less hanging out over the back would be to use a Baja flat Utility Rack, a Gobi rack or any rack with cross boards like I described above.

It you liked picture here's another one : ) My canoe is 16' Sportspal, so I think 18.5' shouldn't be a problem. As per crossbars, I have 58" , but my canoe is a wide one, basically is almost as wide as roof rails. But if your canoes are narrower - 72" crossbars might do.

and sometimes the boat just lives on the car. I can certainly try and look for longer cross bars.
My concern was how short the roof rails are, front to back. I thought the canoes would be unbalanced and stick out too far in the back.
I had thought I might have to add two more mounting points and a crossbar on the front edge of the roof, or remove the rails completely and use mounting point, or get full length roof rails.

Here is a loop solution like Wingsuit is suggesting on amazon

Amazon.com : Sherpak Quick Loops (Pair) : Boat Trailer Tie Downs : Sports & Outdoors

Although Yakima does not list an application on their website, I have found that the setup used to mount a crossbar over the front doors of my 3rd gen works fairly well on the 5th gen. I carry 20+ foot outrigger canoes on my rig using this setup over long distances (greater than 1000 miles). The bar is not an exact fit and has only presented an issue when driving in heavy head or cross winds (35-50 mph) at interstate speeds.

[Edit] I have also used this set up with a Yakima drydock hooked up to the hitch that works well. These are not cheap solutions by any means, but have met my needs.

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