Should I just do all metal pipes then?
I would use that flex pipe if it will would make it a lot easier to install, if the straight metal pipe is easy to install I'd go with that over the flex but really either one will work fine for you. It's just those flex style with wrinkles or groves will probably have to be cleaned out sooner then a smooth tube type, I'd let ease of installation be the deciding factor. If you decide to go with the straight section pipe, I like to wrap the joints with the metal foil duct tape, keeps the fine lint from blowing out into the room, personal preference.
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