I might be incorrect buy my assumption is that he has 2 center braces that would get in the way of the spread if he only uses 2 panels, I was thinking he would need at least 3-120 watt panels for his because of the center braces.
well if the braces will cause shadows then 3-100's would work fine, or 3-150s if the money is there thats a safe bet you'll have more than enough and can crank them up slowly as needed 2-200w works too, I dont think the braces will be a huge issue, these have 90 degree reflectors and so they spread under and around the braces pretty well actually.