Wood framing guys, how can I do this safely?

[Ballistix]

It's not to scale, but 6x6's could certainly be used. I was just illustrating what I was trying to convey in text.
Of course, the center posts would only have a horizontal notch on the one side to fit the dimension of the lumber you use. These are for the corner posts.

 

[hoosierdoc]

Thanks for taking the time to draw that out. I'll use 6x6 corners and a 4x4 in the middle of each length then

Rookie that is tempting but I'm more familiar with wood, thanks