You can make a changes to the system but all you really will find you need will be insulation and bottom insulation a priority as hawghangar mentioned.
You can look at Underquilts, or the supershelter, or pads (even simple ones from Walmart) for underneath you and any sleeping bag for you.
The key to immortality is first living a life worth remembering. - St. Augustine
Some people feel the rain. Others just get wet.
- Bob Marley