Hi Den,
good it's working out for you.
Basically the one BU (blender unit) can be what ever you want. Please, remember the Blender export script export the BU values without any conversions.
So, if you like to have a 1mile * 1mile square object in AH, made with Blander, then the object measures MUST give in feet. I.E. 1 BU is 1 feet means 5280 BU * 5280 BU object.