Will WM Caribou Work With Ultralight Sleep System?

I'm interested in experimenting with an ultralight sleep system, now that I've read a few of Will Rietveld's articles. I'd prefer to keep using my WM Caribou, rather than to buy a new bag. I'm wondering, though if the sewn through construction and lack of an insulated draft tube would make that difficult. Anyone here on BPL use a Caribou as a part of their ultralight sleep system? Anyone know if I'd need baffles and a draft tube?

thanks