All pop-top tents in Buses and Vanagons through 1984 attach to the pop-top via a tack strip and staples. In 1985, Westfalia changed the way the tent attaches to the roof—essentially mirroring the way the tent attaches to the body of the vehicle: via an aluminum strip and sheet metal screws. These two methods are called "staple-in" (up to and including 1984 year models) and "screw-in" (1985 and later year models), respectively.
At GoWesty, we have been involved with Vanagon pop-top tents since the mid-'90s. Back then, we found ourselves replacing tents that were, in some cases, barely five years old. It wasn't because they were worn out; rather, we had been working with a US manufacturer to develop tents that included side windows (in addition to the original front window), and customers were interested in upgrading to the three-window version. We were able to experience first-hand the fitment and function of many factory-installed tents.
One of the things we noticed early on was that getting a tent to fit "perfectly" is just not possible. The original, factory-installed tents didn't fit "perfectly," and there was a high degree of variance from one vehicle to the next. In particular, the earlier "staple-in" tents fluctuated wildly in how they attached to the top. We could clearly see how the installer at the factory had adjusted the installation technique from tent to tent in an effort to find the closest-thing-to-perfect possible.
Another thing we learned during those early years was that if the tent was made a bit too large dimensionally, it could still be adjusted to fit and function just fine. But if it was made a bit too small—incrementally in some of the critical areas, even—it just would not work. The problem was most acute at the front panel and around the bend toward the side panels where the top opened tallest. Even just 1/4" too small in some spots made the tent unacceptably tight—to the point where one could hardly get the top open or, in some cases, would end up ripping the tent while trying.
The result, of course, is that we have always erred on the side of going "too large" to ensure a pop-top tent will fit no matter what. Most customers are perfectly happy with the fit and function of our pop-top tents right out of the box. However, if you are interested in achieving the "most perfect" fitment possible, these are the steps required:
Any of these options represent a lot of work for what most would consider very little gain. Thus, most tents are installed and left just the way they are, and they work great—and customers enjoy the advantages of a three-window tent!
Rest assured, though, that we will continue to strive toward the most perfect fit possible. We consistently work with our manufacturers to identify and correct variations, and every tent is measured before it gets shipped to a customer to make sure it isn't too small or way too big. Even a tent that measures "perfectly" will be affected by vehicle variances that are beyond anyone's control—so don't get frustrated! It's all part of the quirkiness of these vehicles, and we still love 'em.