the hexamid has a cuben groundsheet option that is suspended from the tarp with shockcords, to make a sort-of bathtub floor. If you pitch the tarp lower, it wont make a bathtub anymore. Its heavier than a poly groundsheet, but also much more durable, and easily repaired with a spot of tape if you get a hole. Ive slept on some fairly rock imbedded ground, and no holes yet in my mine. The 1.1 cuben is pretty puncture resistant.
the length of guylines is important on the hexamid to getting a good pitch due to all the fixed angles in the tarp. I imagine it would be more difficult using rocks and sticks to achieve that. Not that it really matters much.
Easy enough to just stake it down. But, the distance from feet to tarp, and nose to tarp, is predicated on the tarp being pitched about 6" above ground. If you are on an air pad and attempt to pitch it tight to ground, the tarp may be uncomfortabley close to you. Propping up the end tieouts with sticks will help.