I have a Hennessey asym and I can tell you that it takes some experimenting to get it right. I switched to a Clark nx 250 which I find to be much warmer. I still like the Hennessey though. They both take some getting used to though. Overall it beats sleeping kind the ground!
I am also trying to tune in my Hennessey. My second time out I found the higher foot hang and also moving both the foot and head end higher (loosening the hang) made a huge difference. Like mentioned earlier, without load the hammock ridgeline is pretty loose and when I am in it (under load) I can twist about a 90 degree twist so it was not too loose.
Nice to see others moving in the same directions and getting the same advice for things I found as well..
I'm pretty new myself...but I will concur that laying on the pad when it get's chilly can be tough. I found I was "bunching up" my shoulders all night trying to make sure they didn't touch the cold sides.
One simple solution is if you have an extra synthetic bag you can put that under you and your pad. Note this is not a lightweight solution, but if you are just car camping anyway then an extra sleeping bag under you will help while you get it dialed in. I did this on a recent trip using a 50 degree bag and it really helped. I was laying on the zipped bag, so I had two layers under me plus my pad. I tried to stay on the pad, but if I rolled off a little or my shoulder touched the side I wasn't ripped from my slumber from "the cold shoulder".
I have had good luck with my Exped 9 down mat. keep it soft and it contours pretty good and is warm