Speed..good link,getting on a sleeping pad is one of those last resort sort of things,i have woke up at night to the sound of a storm and just hunkered on mine hoping there were no local hits.
a poster at BWCA.COM told about a close hit that went thru the roots of a pine he was under and even on the mat he was shell shocked for awhile.it's the one thing i worry about out on trips because there is nothing you can really do about it.

look just to the left of the canoe across the bay,you don't need to be on high ground to take that hit.i would not wanted to be in that camp that day.




closer look---