My 45k Hot Dawg was delivered yesterday and I'm going to install mine with the vent pipe horizontal too. I just ordered a 3' section of Type B DuraVent pipe. I'm going through 3/8" OSB, 5 1/2 inch walls (2X6 construction), 1/2" plywood and 3/4" siding. Modine calls for 1/4" down pitch per...