For my chesapeake 18, I use a combination of the standard bungee paddle float rigging behind the cockpit and deck perimeter lines. Anchor the deck lines approximately 1 ft on either side of the paddle position (fore-aft). When you are in the water, slide the paddle under the deck lines on each side and the bungee rigging. Very secure and I've used for multiple wet entries using the paddle float method. The problem with just bungee rigging is when you are just starting out or having a bad day, they don't hold the paddle securely enough. The deck perimeter lines really help hold the paddle in place especially in roll, but make sure those lines are fairly taunt. 

I made two loops with 1" webbing and side lock buckles.  Loops just behind cockpit.  One on left, one on right side.  Each attached with a screw, nut, and finish washer. Similar to standard hatch hold down. Except each piece of webbing has both parts of the buckle on it with the screw  in the middle.

-Ivan