Here is how sag is taken care of with the Speer PeaPod:
On each end of the pod are nylon cords much like shoe strings, which pass through channels. I wrap these around the hammock end knot
and adjust tightness so that I normally have about 6" of sag between the bottom of the pod and the bottom of the hammock. Also, when these cords are tightened up even a little bit, it causes the pod to cinch down tight onto the hammock ends.
Once I get in, usually the hammock sags more than the pod and I end up with the pod just barely touching my back, no gap. If I want a little more gap for some reason, or if it is tight enough to compress the loft, I just loosen up on one end a little at a time until it is where I want it.
So you might want to add some channels to the ends and run some nylon cords through them. Though I'm not sure if the hood and all would interfere with any of that. But on the Speer Pod, it is hard to imagine a more draft free approach unless you are actually inside a mummy bag or rectangular bag with separate hood. It is draft free enough that small gaps under me don't destroy warmth. But if you have any openings on the end, cold air will rush in to fill those gaps and it will be cold.