Awnings

So I am building three awnings, one for a produce stand, one for a west window and one for a door. The awnings are designed to have an overhang of two feet. The Produce stand awning is 8 feet wide and the other two are four feet wide. They are constructed out of 2 x 4's, with a bottom frame that is 2' x 8' for the produce stand with 2 x 4' s running across the frame 24" O.C. (this will be screwed into the side of the building and sticking out 2 feet). I will then have a top ledger board (screwed into the side of the building, and have a diagonal 2 x 4 running from the top ledger board to the bottom frame and screwed into each with 3" screws. My question is, will this be enough support or do I need to put a diagonal at the bottom as well? I would prefer not to aesthetically, but am wondering if it would be structurally sound enough without it?

Hmmm...my gut says I have to know more about the fastening and connection as well as seeing a plan, end and side elevation view drawings to give a respectable position...

- not much to add here! Just to give a thought to wind shear and wind loading, You don't want part of your unit to come off and damage your neighbors display
or some kiddy ! Big AL