I cannot quite tell from the pictures, what is the stand frame built out of? It looks like maybe painted wood, with the extra panels of metal added to protect the surfaces?
Edit: No, now I'm thinking it's painted steel square tubing.
I like your vent hood design quite a bit... when I get to the point where I need to figure out my ventilation, I'm thinking of asking one of the local sheet metal/duct shops to fabricate a lightweight hood out of HVAC duct. Seems like it would weigh less than the 2x4 + FRP options weigh. I could be wrong.