I donno the answer the your question precisly but on a related issue
I would like to point out that since a lot of people will be playing in 3rd person
mode low cealings and small doors should be carfuly considered.
I have seen a few maps were some of the areas messed with the camera just a little.
Hmmm...isnt the standard player/npc height about that of the NPC entity box?
Try just draging one of those around the map and using it to measure your doors