Just in the nick of time.
 

It was a balmy sunshine filled day at 50*. Finaly got the Calmark cover on our HiLo. Used one ratchet strap(Porter cable) from Sams club. Couldn't use more ratchet straps as the batwing antenna and vents take up the realestate on the roof. Tomorrow the wind is going to be 30MPH with gusts at 60MPH. This will go on for hours.

I like your idea of the ratchet straps, We have been using ropes and trucker elastic straps.
Wind and Canvas don't get along together very well.

We have some older trees in our yard and after a wind storm like you are getting we spend the morning picking up tree branches.

On my 1509 Hi Lo I connect two ratchet straps with the S hooks then place them crosswise across the top. I repeat this with two more. Now I have an X across the top, attach them to each of the four corners. I fine different locations on each bottom corner for the S hooks. The holes at the bottom of my awning work well on one side. When these are ratcheted down tight and in combination with multiple bungees they hold all winter.

My air conditioner cover, sky lights and antenna are covered making snow removal much easier. I live at 7,600' elevation in Colorado so wind and snow are regular events. Several times already this year.

I anticipate larger campers would require multiple tarps if you don't have a commercial cover that fits. I couldn't locate one as I have a rear entrance and smaller than average camper. Tarps from Costco have worked fine and the price is right.

I use this same technique to cover my five foot high house in Tiny Town near Morrison, Colorado though I have to wrap the ends of the straps around flagstone pieces as there is no place to hook these straps. I also use bungees all around this little house.

This system protects both my camper and little house from small branches and hail. Several years ago I had a tree service remove three trees and lots of larger branches from remaining trees. I thought it expensive at the time but now believe it was cheap insurance for my camper.

I hope this helps someone on this site. I wish I had joined this forum years ago as I have learned a lot of useful information every time I read comments by everyone else.