Yo

I built a recovery after Morris. I went for the thin 3/4 x 6mm ribs because that was the way my recycled oak bed head 'rib stock' was going to be best cut up. I spaced them at 3" and was happy with the result.

[6 mm was the width of my router bit]

Only slight annoyance is that it helps alot to put a snow foam mat on the floor of the kayak to help my heels slide over the ribs at the 'tight points' when I get in or out of my recovery.

Here is my website address of my build with more information than you need to know. Read only if you want to go to sleep . Next time I would make my recovery a bit wider. Present one is only 22" and a bit tippy, next one would be maybe 24" - 26" wide.

http://piratepetester.googlepages.com/recoverysofbuild

Good luck Pete.