Here is my old setup upon my old car - EG5 civic , on bilstein adj. dampers - lowered 2.25inches. As you can see , underneath - with a underaxle setup - left approximately 1.5inches clearence under the lowest point !!! Bah ! TOO low ! LUCKILY it was just under the axle- so most bumps could be avoided.....

Dayum ! IF u must go underaxle - dont lower ur car