You should only need two straps per side. Here's what I do with whitewater boats and a vertical stacker system. Should work similarly with 10 foot rec boats.
Stack all of the boats for one side up on their edges, and run a single rope or strap from each stacker over the top of the whole stack and down to that stacker's bar. Do the same on the other side.
Attach bow and stern lines as insurance policy, especially if you're carrying 6 or 8 boats this way.
Kayak Deck Gear Bags
Pull-Up Strap Handle Kit
|Table of Contents|