and you have a small laundry room, do you pretty much need to replace the semi-rigid 4" duct that's clamped between the dryer and the inlet of the vent?
I was at home depot today, and read that those flexible ducts aren't meant for dryer vent applications, so it seems that if you have a tight laundry room, the semi-rigid 4" duct will probably get destroyed when you pull the dryer back.