Next, you'll place one of the 1.5" pieces of pipe inside the 90 degree sanitary elbow. From there you'll attach your 2nd 90 degree sanitary elbow, making sure its pointing up. Attach the 20.5" section of pipe to that, and finish it off by attaching the last 90 degree sanitary elbow so its facing towards the back of the unit.
I have a rear windshield, is mounting the pipe any other way will be up to you. For those with rear windshields, you'll want the mount at lease three or four inches from the bottom of the top elbow. Make sure its centered and the pipe is straight, mark it, they drill a hole and use your conduit bracket to mount the pipe to the windshield. Again, make any final twists and adjustments so everything is straight and looks the way you want it. Using a sharpie, make alightment marks on each joint, and number each joint so you don't get them mixed up.
You're going to assemble this into two sections. The first section will be (in this order) the coupler, 7" section, 60 degree elbow, 1.5" section, 90 degree sanitary elbow. The section section will be (in this order), the 1.5" section, 90 degree elbow, 20.5" section, and the 90 degree street elbow.