Design Rationale: 6 - 8 inches ground clearance

The Sport Cycle has about 4 inches of ground clearance. Last summer, I built a Marauder recumbent bicycle as designed by http://www.atomiczombie.com/ It had 4 inches of ground clearance and it dragged when I rode it over the hump where our driveway crosses an irrigation canal. I modified the frame to 7 inches of ground clearance and that seemed to be a good number.