How flexible are these lint eaters for pipe on the brushes? I have a 3" exhaust port expanded to 4" up the flue. So, i need something that will do mostly 4" pipe, but will also fit through the 3" opening at the beginning. Further, i'd like to go through the trap door if possible, which honestly doesn't open that much.... maybe an inch on the non-hinged side. Will a 4" work?