I have mine in a corner of our garage and have it about as tight to the back and left walls as possible.
I wouldn't make anything smaller than:
Height: 74.5" ( depends on what riser, motor, etc you have )
Depth: 45.5" ( Including the prox sensors CNCRP sells )
Width: 70" ( That won't allow the doors to open on the CNCRP control boxes )
Hope this helps.