[Jeffrafa]

I think part of why FIRST does not explicitly specify all dimensions, such as the distance from the pyramid to the end of the field is to minimize the critical dimensions that teams may hold them accountable for. Repeated setup and teardown of such a large assembly of parts such as the FIRST field cannot guarantee an exact dimensional consistency throughout dozens of events.

They even clearly state in the 4th paragraph of the Arena section that they will try and make the field configuration as consistent as possible from one event to the next, but guarantee no better than 1/4" tolerance on large field assemblies, and 4" tolerance on gross field dimensions.

So you can calculate and work off of the nominal dimensions, but it would be smart to make sure that your design can tolerate some variability.