Well, 2 nights of testing down, many more to go!
Night 1 was ~42 degrees w/5mph wind
Night 2 was ~20 degrees w/3mph wind

Here is my setup and some observations.

HH Hyperlite
JRB Nest
30 degree down bag (Marmot)
stock tarp
small pillow

Clothes Night 1
Capaline 3 base layer
hiking socks
Summary: I woke up in the morning nice and warm, I guess this is dialed in!

Clothes Night 2
Capaline 3 base layer
200 wt Fleece layer (pullover & pants)
hiking socks
Summary: Cold spots woke me up around 2am (16.8 deg f with wind chill )

HH Hyperlite: my first thought was, there is no way this line will hold me, second thought, there is no way this material will hold me, third thought, there is no way this knot I just tied will hold me.
At this point the only thing I'm worried about is my knot. Quality is very good, besides a few odd stitches here and there, nice and solid. Overall, I'm very impressed with the Hyperlite.

The tree huggers are too short. In order to set the hammock up per directions I had to bypass several well oriented sites because one of the trees was too large. If you just pass one of the ends through one of the end loops and cinch it around a tree, they are long enough, but I'm not sure this is a good long term solution as the full weight of the hammock will be born by each loop sequentially instead of both loops simultaneously this would double the force on the webbing loop stitching. I'll be looking for alternatives here.

The Tarp Quality is high. You can attach to the ridge line quickly and easily or use the tieouts to raise or lower the tarp from the hammock.Overall, a good tarp as designed
as mentioned on another thread, the stock tarp seems small. I'm not sure I fully agree here. If I were just hanging the hammock, I feel pretty confident that I could fully protect the hammock from wind driven rain. The setup allows for a nice close pitch of the tarp to the hammock and you can really snug it down to weather proof your setup. But, with an under quilt attached, and a down one at that, I worry about the foot end being too exposed. By moving the tarp down towards the foot end I was able to get passable coverage but I wouldn't trust it in a real blow and will be replacing the tarp for my hike. Nothing really wrong with the stock tarp, but I would like some extra 'living space' and gear protection for my 'home' this summer.

JRB Nest It keeps lofting, and lofting, and lofting. Quality is first rate, nary a stitch out of place. I still do not have the setup of this quite dialed in. It seems that I had a air gap at the foot end and it too tight in the mid section. Overall, I was comfortable at 20 degrees, some spots were iffy but between the hammock sagging (its brand new) and learning to set it up properly, I am confident I could be very comfortable to 20 degrees with this down below.

Marmot hydrogen (30 deg down) awesome bag, but as a top quilt, not so much. Plenty warm, just not being used properly here, the bag is a mummy type with a head pocket...when used as a top quilt the head pocket becomes a face cover...which your breath gets wet quickly...which gets cold quickly. I would say the bag is true to its temp rating.

Staying warm or not being cold
My feet got cold quickly so I tossed some spare clothing under them and they were better, shifting clothes resulted in cold feet so solution is still TBD.

Cold shoulders and butt. At 2am (~21 degrees w 3mph wind) I woke up and the outsides of my shoulders were a bit cold as was my butt, I'll probably end up using my ccf sit pad under my rear. I'm contemplating making a mini-spe that would fit the sit pad and 2 wings for use 'waist-up'. I'll wait for the hammock to settle and try attaching the Nest better before launching down this path as I'm sure this would be detrimental to the comfort of the setup. I placed my fleece gloves and a thin sleeping bag liner under my rear that I had brought out 'just in case' and slept well until morning. overall, not bad.
As to going lower, with an April 1st start date, I feel if I can get to 10 degrees comfortably I should be ok. I'm considering making an over & under cover for the early going. I'm not sure what this will 'add' in terms of warmth, but will probably help if there is more wind.

YMMV About me, I don't mind sleeping in the cold, in fact I sleep better in the cold, my wife says that I am like sleeping next to a heating pad during the winter. Winter in our house (62 deg) finds me with a sheet, light blanket and a pair of boxers and happy as a bug in a rug, so your results may vary!

--Brian "Cargo" Nobo April 1st