32 game units = 1 meter. Make corridors 6-8m wide, and 5-7m high, doorways ~4x4m. Avoid straight sections longer then 40m. Player class sizes are in the "Starting Tremulous Mapping" guide (some classes are slightly diff size in 1.2). I think ATCS base rooms are about 24x30m, lower floor 4.5m high and upper ~6m high, you can use /viewpos to get your coordinates in-game, and use that to measure how big something is.