For a canoe or kayak I'd be caught using foam blocks. A foam block set is about $40. I haven't tried them but it seems they'd spread the weight enough that you wouldn't damage the coachroof.
If you go with Thule, you'll need their tall #387 feet and the 65 inch bars. You can use a Hull a Port for a kayak. Canoe you can carry upside down on the rack.
In any case the boats will be way up there!
I have 4 boats, including a CLC tandem and they are on a trailer. Beats lifting them up on a roof rack!
1966 109 5 door wagon 300Tdi "spermaceti fueled"
1994 RRC LeWiB "ruining the air behind me"
1968 2A 88
All my troubles are Rover