two pads (and the sleeping bag), I can't feel the hard surface of the cot at all when I'm laying down, so I'm good to go. I sleep really well on that set up.
The other trick is that I made wide shims out of 2x4's (and I sanded the edges to make them round and smooth). I have a hard time sleeping with my head downhill, or when I feel like I will slide off the cot in any direction, so I level my cot with those shims. They work great.