New Wanna-be- floor 1x2 or 2x2?

My wife and I fell in love w/teardrops last weekend and want to build one. We are just planning now (yeah right honey) but I have a question on the floor. I see plans w/1x2 or 2x2. 2x2 seems like there would be more to screw the sides to but I never see teardrops blown off alongside the road. Any suggestions?