I had the windshield installer also install the hatch and quarter windows at the same time. For prep, carefully check for any voids on the border of each window opening and fix. Check the edge at the bottom of the hatch glass so it will fit evenly, mine required some filling. Mount the hatch on its hinges but not the gas cartridges yet. The top edge of the hatch glass is critical since it can scrape the roof when opening so make sure to have only a small gap at the bottom edge. No weatherstrip is used because the glass is laid on a bead of black adhesive. My installer spent a lot of time cleaning and prepping the surfaces before he carefully laid down the bead, then applied the glass being careful to align it and keep the height correct.

I suggest that you talk to the head of the glass company so he will realize this is a special job and send his best installer. You'll probably have to assure him that the glass is all DOT approved, which it is. In my area, there are quite a few sleazy auto glass companies that offer restaurant coupons, $100 bills, and other hooks to get business. For my roadster, daily drivers and especially my 818, I've had Safelite do the installation since I know they are reputable, though maybe more expensive. I think the installation of the 818 windshield, hatch and two quarter windows cost me $400, plus $50 tip, but I've tried to forget most expenses.