After some thought I think my cold spot might have been caused by the pluq bunching towards the center, causing the part near my butt to sag a little too far away from me. I can see the advantages of corner tie outs in that regard, but I do like the ability to slide the quilt along the suspension once I am in. If I was going to go to the trouble of adding draft tubes, I think I would just make a down UQ
...if sag is what you think may have been the issue, then just add some grosgrain ribbon to each side of the center with shock cord tied to it, and a mitten hook on the free end. Shug has a video some where on this. Then once your in your hammock and slide your UQ to where you want it, reach down and then attach your shockcord to your ridgeline. It pulls up and keeps it there. Hope that made since. It's an easy fix.
By the way, draft tubes will be easy for you to do. K.I.S.S approach to them.