[GaryVoshol]

There may be some slight imperfections in the liner or the carpet underneath it, so you don't want to plan on extremely small clearances. The field surface itself is pebbled, but if you're trying to hug the ground so closely to have that be a difference, I'd say you will be having other problems with your clearance. You can't design so closely that the slightest bend in your frame from a collision means next round you're scraping the ground.