Thanks Ken, that looks like my best option. I use a similar temporary set up when I rack a second yak, guess I'll make a permanent version...

: I have a thule rack also. I made cradles using a couple of blocks of
: minicell, 3" x 3" x 16", with a slot routed out of the
: bottom (slightly narrower than the thule crossbars so they fit snugly),
: and with the top surface shaped to conform to the hull of the kayak. They
: took about 5 minutes to make, total cost under $9 Cdn for the pair. With
: loop straps over the top, and bow and stern lines, the same as you'd use
: for Set2Go cradles, this setup is very secure at highway speeds.

: Ken