I think I have settled on bladder molding a two part wet layup for the duct. I need to figure out a way to make a reusable and sturdy bladder. Ideally out of silicone. Rotomolding is an option but I would have to build a machine to be able to do it. I wonder if I can sneak perforated peel ply and something absorbent into a stack between the bladder and the carbon to pull off some excess resin.The other option I was looking at was oven curing with a silicone plug inside the part that would expand and create pressure. My garage is ~560 square feet and I have to be really careful about taking floor space. Safe ventilation would be an issue since my living room and kitchen are above it. I am also not sure how easy it would be for me to get the silicone part back out with the shape of this part. I do have a fireplace in the garage I could run aluminum ducting through...