This question comes up fairly often.
The Westfalia top is fiberglass with two layers of wood inside. This makes it a MUCH more durable top than the Winnebago plastic top. For this reason it supports roof tracks really well.
I prefer the tracks over "artificial gutter mounts" because the tracks allow for a wide range of adjustability, look like a factory install, spread the load over a greater distance with more attachment points, and provide options for things like solar panels.
I've always used the 60" tracks to get the most coverage.
Mount them about a foot from the rear of the top. This puts the load near the rear of the top to make it easier to open. But also give plenty of reach towards the front of the top. No reason to be clear at the rear of the top.
The tops get really heavy, really fast. So you may want to add extra gas struts to the top to make it easier to lift with a load.
I mount them 36" apart. This puts them in the ideal support range for the cross bars. It also puts the trans near but not directly over the edges of the top. It also clears the hinge mounts.
The stock Yakima bolts that come with the tracks are not long enough. You will need to replace them with at least 1.4" bolts. I use stainless steel to prevent corrosion. Make sure the heads are no thicker than the stock Yakima bolts. These are easy to find at any ACE Hardware or similar.
Use a good outdoor silicone. Make sure to spread it on the holes before putting the bolts in. This will ensure a watertight seal.