Hey there. I too have basically the same set up, Expedition soon to be 2QZQ modded. I am about to pull the trigger on a Mally Mac IX Shamu. I saw a thread around here with people claiming the Shamu was good for them down to 30 degrees if I remember correctly, maybe it was even 25 degrees.... Molly Mac also sells IX inserts that claim to bring you down another 10 degrees. So if your going by website temperatures thats 30 degrees with a Shamu and one IX insert.
I believe they work well on all gathered end hammocks, and I remember watching a video on you tube filmed by the creator where he was with his friends and he said he was going to extend the sides another 8 inches total to hug the asymmetrical design better.
For me, I plan on using the Shamu and a therm-a-rest which I bet will get me down to 25- 30. Perfect for me for now...till I get more serious about winter hammock camping. I also have a very nice down jacket which I have never been cold in....that will be a great help too.
I have subscribed to this thread to see more responses with this direct question that relates to me as well. I need to read and research everything before I can make a purchase, it may be a sickness...haha. Takes me forever to pull the trigger to buy something...but with this, I am verrrry close. Safety is off!