[EricH]

Originally Posted by Van.Augur

Time to play devil's advocate:

If you want to be exact, you might want to take into account that the rough terrain, according the rules, is a random layout of the steel cubes. There are an extremely large number of rough terrain defenses that could theoretically exist (keep in mind they aren't symmetrical when you rotate them 180 degrees), making the real number of possible unique defense layouts impractically large...
but still calculable

Nice try, go read the field drawings. All the rough terrain units were built the same. "Random" was in fact in quotes in the Manual. You only get one rough terrain defense, not one per combination...