Hi bestgrow,
Thats not a bad layout, one of the best is to use multiples of this. O = Bulb X = Plant
O X O
X O X
O X O
bgmike8 its horses for courses, shades have to be used for Flat SOG grows as vertical bulbs have to be hung between the plants for them to be efficient.
It really comes down to what your preferred style of growing is, 1.5 + gpw can be achieved from a tree grow of just two plants using vertical bulbs. It is also quite easy to get the same number from a flat SOG but obviously you have to use a greater number of plants.
Another factor is if you combine sog into a vertical grow and use vertical bulbs you can achieve 2+ gpw, so as you can see there are many factors involved not just whether or not to use a shade.
Heath