Quick Hood Loops, Mind and Action Kayak Tie Down Anchor Straps, Canon Transport Accessories for Car Hoods and Trunks (2 Pack)

This is how I do it with a Prius and 17.5' Coleman. Grab a set of thesefor your bow lines, they work great. People like to talk crap about these foam blocks but as long as you tie everything down properly it's no less secure than a roof rack. Take it slow the first time and keep an eye on your thwarts, mine sticks up about an inch proud of the gunwales, so I have a nice scratch in the middle of my roof now.