My experience. Don't use ratchet straps, it's too tempting to over tighten. Some sort of gunnel bracket is important. 2 diagonal bow ropes really help truck wash. I fasten the front thwart to the front bar with two small ball type bungees. this secures against fore-aft movement. Maybe overkill, but I drive secure.
Very much the same here.
I’m a rope guy, and prefer good quality rope to cams or ratchets. I know by feel how tight a trucker’s hitch should be pulled.
Gunwale brackets or stops are an important piece of securing a canoe on roof racks, combined with two belly lines and bow & stern lines.
When I most often carried a single canoe I used two diagonal bow lines, which if positioned and tied correctly prevents any sideways movement of the bow overhanging the front crossbar. But when carrying two (and sometimes as many as four) canoes on the roof the mass of double bowlines is like peering through the windshield at loose macramé.
With two boats or more boats on the tracks I use single bowlines, but still tie them off on the diagonal for better visibility.
Belly lines and gunwale brackets will prevent the hull(s) from moving sideways, and a bow to bumper line will keep boats from moving back. But moving back is less of an issue than the hull moving forward, especially in a panic stop or hard brake.
The bowline(s) typically pull forward. Unfortunately the usual position for stern lines is also pulling forward. Having the bow and stern lines springlined, pulling in opposite directions (bow line forward, stern line back), prevents any movement.
I don’t trust a bungee for that heavy duty and secure the stern painters with a trucker’s hitch between thwart and rear crossbar, so that the stern lines are pulling backwards. On the truck that has the added advantage of not occluding the tailgate and cap door with ropes for easier access.
Some restraint preventing the boat from sliding forward is critical. If you’ve ever locked up the brakes with boats on the roof you know what happens. The shorter the crossbar spread the more likely the hulls will end up as hood ornaments. Think something like this =()=
On the whole I’d prefer that the rear-pulling lines be somehow attached to the vehicle/body and not the roof racks, so I had belly lines tied to the roof rack crossbars and bow and stern lines tied to the vehicle. That’s something else I need to figure out/retrofit on the Tacoma.