TL;DR
instead of 4 fluidboxes for pipe, just do however many are needed.What ?
above ground pipes connect on 4 sides, and have 4 fluidboxes even if only 2 are used.underground pipes have 2 fluidboxes which are typically always used but don't see why a disconnected fluidbox should be considered, either.
perhaps they can be allocated as needed when adjacent pipes are placed.