Ok, caveat- I Is A Rank Amateur, with virtually no experience blacksmithing.
However, thanks to some help from Pep Gomez, I did get my Centaur Forge (an older, custom job, but basically exactly the same as on their web page) lit (yeah!) and I noticed that the 3 feet of 8" chimney pipe I stuck on the hood DID draw quite a bit of smoke.
There was still a lot of smoke escaping from under the hood, esp. with the blower going. But in my inexperienced opinion, the chimney and hood combo did help.
Hood seems virtually useless without some sort of chimney.