I know we are supposed to leave straight pipe on the last 3 feet of duct run to the cyclone. I have a brand new cv1800 with the 6inch s&d inlet. I've been told that I will benefit from running my main trunk line in 7" duct ( I'm running thick gauge metal pipe ) however I'm concerned that running the 7inch and reducing at the inlet will cause too much turbulence and reduce the amount of separation capability. Am I being too worrisome ? Any advice including speculation is helpful. Thank you all so much and may you be safe in this trying time.