I'd use a pad if I were you, simple foam is better than nothing.

http://www.rei.com/outlet/search?cat=22000001&cat=22000021&cat=29340995&jxSleeping+pad+type=Foam+pad&hist=cat%2C22000001%3ACam ping+%26+Hiking^cat%2C22000021%3ASleeping+Bags^cat%2C29340995%3ASleeping+Pads^jxSleeping+pad+type%2C Foam+pad