April 1st-ish. Sleeping in a Dreamhammock Thunderbird 11 footer, under a 12 foot HG cuben tarp with door flaps. Insulation is a HG 20* Burrow, with an Underquilts.com Foyle that has about 10 ounces of 850 fill. I'll also have a Mountain Hardwear Nitrous jacket, some sort of midweight thermals, and my other clothes with me. I've also got an Exped Synmat waiting in the wings in case I decide I want that for specific sections - the Whites, in particular.
One thing I've done recently to combat cold head syndrome while quilt sleeping is adding a fleece hood to my overall clothing system. I've taken to wearing this instead of a warm hat even, unless it is really cold and both are required.
If the weather is really piss cold, I might pick up a Nalgene at Walasi-Yi to have a hot water bottle to sleep with. I'm hoping that sleeping in all my clothes with all that down will keep me warm enough, though - and there's always crunches and push-ups to give me a boost when needed.