Bungies...

Get a rope....

Stopped using then dagblasted things years ago.

just as quick once you get used to it, holds better too.

 

But it looks #### good going down the road!

That was a steel tarp, but still 4' side drops.

 

Oh, always go behind the rub rail with bungees. It's more of a pain in the ###, but it looks more professional and you don't scratch your DOT tape.

 

Once you learn how to use rope it'll reduce flapping more than any bungee will. A bungee will always stretch under pull from a tarp, since the wind puts a hell of a lot more force into it than you'd want to unless you like getting d-rings replaced. Once you've got it hooked or threaded through the rub rail give it a tug at every turn front to back 2-3 times with a bungee pulling the slack out at the back before you tie your knot.

I prefer going low to the rub rail when hooking d-rings and eyelets, since it forms a better seal against the trailer. I'll throw a few up higher as well for irregularly shaped loads to take some slack out of the top.

No matter how many bungees you throw on the tarp is still going to flap if you're getting tons of air under it in the front. Make sure you're forming a good seal at the front after you've got all four corners pinned. A 96" 4x4 rolled up in the tarp a few times then sucked down with a strap usually does a good job of this.

Some people will throw straps over the tarp in high sag areas, but I've seen this tear up tarps too many times. Use bungee rope instead, and it'll help suck in a bit more slack as the tarp goes down the road rather than rubbing all the vinyl off it like a strap would with slack.