"Built mine with 50 feet of 1/2 for about $60"
Now I don't feel bad buying a 50' 1/2" ic already made for $85 on ebay shipped. Since I would have had to buy a torch and such to put it together, $85 isn't a bad deal for not having to F*CK with it.
I would maybe get 2 inline 4" fans and exhaust out both of those ports and either leave the door open or install a square vent in the bottom half of the door so it could stay shut if that was needed.
"Those holes to the outside are 4" in diameter and go through almost a foot of concrete as they're in the house poured foundation (this is a basement room)! I have no idea how I'd enlarge those or if I'd even want to attempt something like that. Crap."
I bet a convict could do it with a tooth...
4" vents are pretty constrictive. I would make them 6" or 8" for better flow and less noise, if possible. Especially if you put in a 400 cfm vent. A nice large stainless hood sure would look and work good in that room with those blingmanns...