Here is a link to some Westfalia Add-on Poptop installation instructions
as provided with the kit for the top. It shows that only a small hole is
cut in the roof skin. The top kit does not necessarily include an upper
bed. That is a separate option.

http://www.t3-infos.de/images/Mosaik-Joker_Aufstelldach.pdf

An upper bed is the complicating element if required. The stock camper
upper bed folds the forward wood and foam piece over the back foam
section when the top is down. There is not enough room for that second
layer of foam with the higher arched passenger roof so the forward foam
piece must be stored in some other place.

Mark

Alistair Bell wrote:
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> I still have not finished the top bunk. There is a wrinkle when doing the hole in roof method and that is the top bunk is now on top of the curved tintop roof. This reduces the bed to pop top ceiling distance and the fold up part of upper bunk will not clear. So you have to come up with another solution - the mosaik kit (westy built kit) solves this with a hinged, two part folding out part of bed.