adding an awning to a cargo conversion

Hi Guys
Have been told I need an awning rail for my cargo. where does that connect. Above or below my drip rail..Then does the awning unit slide in to that drip rail and is that what holds the unit in place. Have a 12ft side, should I get a 12ft or smaller that the full side.
Has anyone installed one yet. What did you buy and are you happy with it..Looking at Carefree, none electric and eventually adding an add-a-room
Cheers
Al
Have been told I need an awning rail for my cargo. where does that connect. Above or below my drip rail..Then does the awning unit slide in to that drip rail and is that what holds the unit in place. Have a 12ft side, should I get a 12ft or smaller that the full side.
Has anyone installed one yet. What did you buy and are you happy with it..Looking at Carefree, none electric and eventually adding an add-a-room
Cheers
Al