I live in Alabama, so I'm in an area that's perhaps a little warmer than Arkansas, though not much.

I take my woobie (a.k.a. poncho liner). It' stuffs down pretty small in my backpack, especially compared to my down and synthetic cold weather sleeping bags. It's warm enough for late spring through early fall trips in the southeastern US. Paired with a poncho, it's a very versatile shelter system. I didn't serve in the military, so I bought one online from a surplus store. I see why soldiers and Marines love their woobies so much.

Barring that, one of those fleece sleeping bag liners or even just a sheet is a great thing. I personally would go with a queen or king size sheet just so I had more options, though it would definitely be heavier than a twin.

Just my two cents.