I was planning on ending my ventilation with a 8" muffler silencer (8" for the airflow with a 10" round pipe on the outside) but I can only find the outside pipe in 5' sections. If I have to cut the 5' section back to 2-3', I will but if I just use 6" for airflow and have an 8" outside pipe on the muffler is that Going to cancel out any noise reduction I gained from the oversized insulated ducting? Hope that makes sense..