I believe that you will need to use an awning similar to the one below, it is a Carefree Campout. I believe the side rails fold into the roller for storage and the only parts that are attached to the trailer are the main roller across the top and the brackets that go on the sides to secure the side rails when the awning is extended. This should allow for the largest awning without the location problems discussed above. It is also less expensive than the normal awnings.
You can go to the Carefree of Colorado website and look at the manuals.
2005 Safari Cheetah 38PDQ - 2009 Ford Flex
Me (Gatogonow), The Boss (DW), Honey Bunny, Maggie May and Mollie Kay (The Gatos)!