hello, I am in the process of running the intake venting for my pellet stove, and I have come across an issue. My pellet stove have a 4" intake and I am running it straight down into our basement, then a 90 into the crawlspace and then another 90 to the exterior wall. My problem is that the length of venting is approx 12-15 ft combined with 3-4 90 degree bends will be to long and will cause combustion problems. I was thinking of increasing to 6" when i get into the basement or crawlspace to help air flow. Will this help at all or would i just be wasting my time? Any help will be appreciated.