When you start a new scene. Go into the unit setup section under customize and set either:
Display units to meters and system units to centimeters. Have the gris set up for 2.54m which would represent 1 segment in the game engine
Or if you want to use english measurments set the
Display units to US feet w/ Fractional inches and the system units to inches. Have the grid set up for 8'4" or 100" which would represent 1 segment in the game engine.
Pick one to use, then import your model into the scene and scale it from there. This should get you pretty close to the right size. Do keep in mind that everything that is stock has been scaled down to 80 in the FPE files.
Hope this helps.
