The problem I see with making any exhaust pipe of significant length or size is vibration will soon fracture
a solidheader joint. If instead, the connection is made with something like silicone between header and pipe, seems to be OK. As to that air can, instead look in womens hair care products and you will find any shape you need. Saw one Sunday, aluminum, 2"dia.,9" long and had a screw on cap appx. 1/2" in dia. Looked perfect for a mousse can project. Good luck, red