.....cutting a giant hole in the roof of your shiny new van to install the PH can be a bit stressful....getting liquored-up first helps quite a bit....
Seriously, a good point is that over time no matter what you build you'll want to change things after using the van for a while. I'm doing that as we speak.....adding more storage.
Also, many sub-projects have minor (or sometimes major) snags where you need to re-think things somewhat, or order parts, etc. Having 4 or 5 sub-projects going at once keeps the momentum going and keeps the project moving forward.
For example, presently I am:
re-working one of the cabinets in the van for additional storage
I have the propane tank mounting half-baked
Ordering speakers for the doors (this will be a somewhat custom deal)
Sizing up a fresh water tank and determining where to mount it
Trying to determine the best place for the propane heater-inside or outside
building a side door galley
etc, etc.....there are a few more small ones as well.
The projects all start and stop but over time they get finished.