When I deployed for Desert Shield/Storm, I ditched the bag (I, too, remember Korea in the winter time), and took two poncho lines, had one sewed up and a velcro opening added, and bought a gortex bivy from Campmore (not sure they're in business any more). I added a sheet also sewn up (not all the way) and layered the entire set up as the temps dropped below freezing (yes, it gets cold in the desert at night). If it really got cold I'd just put on my wool knit cap and wrap my field jacket around my feet. I was never cold sleeping, and the entire set up was light. Now I find that the Army uses the same system (with different components, of course, and skipping the field jacket around the feet!).