Ralph- not so sure about a tandem wing config. You do get twice the wing area, but the rear wing will see lots of bad air from the front wing, so I'm not sure how much extra lift that will produce. Also, in order to strengthen the fuselage you might have to add too much weight. The last few years we used a light carbon tube for our empennage and the tail vibrated like crazy. To fix it, this year we added almost a pound worth of carbon.

Biplanes are a good solution, but again you have interefence cutting the lift and lots of extra drag and weight. I guess it's just up to the teams to decide whether to play it safe or try one of these configurations.