If you're a side sleeper, I'd definitely go with a Neoair. I personally would get one of the other variants (more R value) so it would be more useful in future trips that may be colder. My original (R 2.5) has been fine on it's own into the 30s. I have tested it as low as -2 with the addition of two blue foam pads (and more clothing as my bag is only 20F as well).

If you're a back sleeper, the Scout should be OK. It's heavier and takes significantly more volume.

You should really visit a store that has pads like this so you can see how they feel to you. I don't mind the horizontal baffles, but some like OregonMouse do.