Roller awnings

I am trying to attach an RV roller awning (this - http://www.ebay.com/itm/Carefree-RV-Awning-15-Rose-complete-with-arms-/110859770849?pt=Motors_RV_Trailer_Camper_Parts_Accessories&hash=item19cfc1dbe1&vxp=mtr) to a 7x16. But how would you connect at the top for the arms?? The only thing I can think of is bolting a vertical plate (~3-4" wide) at the top rail (trailer) that extends above ~ 1-2" and then bolting the arm carrier to that.
I am also going to build a metal carrier rack (canoe rack) on top ......ya'll have some GREAT ideas....

I am also going to build a metal carrier rack (canoe rack) on top ......ya'll have some GREAT ideas....