The only issue I've had is during a driving rain storm the water running up the deck pushed the cover open. Luckily, it never came off.

I have the DOT 1/4 turn fasteners along the front and first couple down the sides, then snaps to the back and bungees hooks across the back. I trailer all over like that and have had 0 problems.
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Thanks to all. I ended up getting 4" preservation tape from Dr Shrink. Taped the cover down and drove 850 miles with it pouring rain and had zero issues.

Thanks again!

The answer to this question is simpler then tape, straps, and fat chicks...don't put a cover on.

On a more serious note, we never tow with a cockpit cover. even if all sides are taped, the cover will still chatter in the wind ultimately scuffing/damaging the paint. leave it off. even with a rain storm I rather have the cockpit wet then ruined paint. the only part of the boat that makes sense to cover/tape is the keel and hull where rocks can potentionally hit.

My 0.02