You may be interested in one of these:
US Army 4 pc Goretex Modular Sleeping Bag System (type that into google or at ebay)
I don't know much about using these on camping trips, but I used the heck out of mine overseas. I'm 6'-0" and about 250 and didn't have any problem fitting in one of these, but I also know there's a big difference between 6' and 6'-5". I'd try one get your hands on one of the military modular sleeping bag systems. It comes with a light bag, heavy bag, gortex shell, and a compression sack. It's a combo that's hard to beat and they are worth whatever money you spend on one. It's worth a try.