As many have stated before, dont get hung up on the whole WPG thing, its more about intensity and spread.
I run 2x250W XM10K in Lumenarc III"s with 420W VHO over my 225gl.
That puts me at 4 WPG.
But Im sure I could have the same growth with out my VHO's so you could say I can have a WPG of 2.2.