Not quite sure what your issue is. I have a dryer hooked up to rigid galvanized steel piping, with two bends before it exits outside through the sill beam. Attaching was very simple, I simply purchased two adjustable bends which can be rotated in three dimensions. They have standard couplings to 4 inch galvanized pipe, which is push fit, followed by taping with aluminum tape (no screws which can attract lint). One of the bends goes on the outlet from the dryer, and one goes in about three feet from the outdoor exit. I put the pieces together one at a time, and adjusted the bends to make the fit work correctly. Certainly it would have been much more difficult, maybe impossible, to make my setup work with rigid ninety degree bends.