I've been playing around with different combinations gear and last night I wanted to test the lightest combination I have.
My gear locker has a lot of ground camping pads and I wanted to get that in the mix. I have a Prolite extra small torso-length pad that is about 10oz and it stows smaller than anything else I have found. I have a Z-lite pad and a bunch of bulk 5mm EVA blue foam.
I have a Hennessy Expedition hammock and a Grand Trunk Ultralight that I have upgraded the suspension on. The GTUL is about 16 ounces with carabiners in the end channels, whoopie slings and Hennessy tree straps and a couple more carabiners. I could eliminate the biners, go with lighter straps and use toggles if I really wanted to get it light. But for testing, the suspension was fine. The GTUL is really comfortable for a such a cheap hammock, with a slick polyester fabric that is very breathable and soft. It is great for a nap on a hot summer day.
So I rigged the GTUL under the Hennessy Asym tarp and tried the pads. It was a wiggle fest. I'm just not impressed with the feel and fiddle-factor of foam pads on top of a hammock. The Prolite felt the best and I understood the size limitations. The shell on the Prolite was easy to move around on the slick GTUL fabric. I added a Z-seat foam sit pad for my feet. I used a Cocoon Ultralight inflatable pillow.
For my ultralight test, I used a Mont Bell Alpine #7 bag that is a 50F rated 16oz down bag with the "hugger" feature with elastic in the shell and a big drawstring opening at the top-- no zipper.
The low was 49F and about 80% humidity, with little or no wind. I was wearing light fleece pants and a long sleeve polyester base layer top. No socks.
I got in an wiggled the pad around, finding that the valve poked me in the shoulder. I finally got it up high enough to clear. The Z-seat pad on my feet was okay, although the open-topped hammock and slippery cloth could allow it to escape. Same with the pillow. Once in place, the Prolite felt pretty good. It is 20" wide maximum and I think the taper and rounded top and bottom edges helped keep it from buckling and making lumps. Of course, it only covered to the edges of my trunk and not my arms and outer shoulders or head. It made a minimal intrusion to the comfort of the bare GTUL.
I woke up about 5AM with the birds singing overhead. My sides were cool and there was some dampness on my back. My feet were a little cold, but I'm sure that just adding socks would have taken care of that. I wouldn't want to tackle anything colder and I wouldn't rate it as a good night's sleep or rave about comfort.
So I got up and had a cuppa coffee and got out my silnylon poncho/undercover and the space blanket/polyfil under quilt I made. The 104" long under cover was perfect for the GTUL and when I pulled in the side shock cords in the UC, the top came up and over the sides of the GTUL. I put the space blanket UQ between the hammock and UC and got in, using the pillow and Mont Bell bag.
Night and day difference. I could feel the warmth off the space blanket right way and the outer cover blocked the light breeze and kept the warm air below. I think the breathable fabric of the GTUL and the airtight silnylon UC worked well together. The UQ is an envelope, so there are two layers of HeatSheet space blanket with 1/2" of polyester batting inside. I spent another 3 hours in the rack. There was nothing to detract from the comfort of the hammock fabric and I was warm and dry. I could lie on either side and position my legs wherever it suited me. After 3 hours, I put my hand in between the hammock and the UQ. It was warm and I could feel moisture in the air, but there was no condensation on the space blanket or the hammock. I think I could take this system to 40F with socks, a foot pad, a fleece top and a beanie.
GTUL with suspension: 16oz
Mont Bell bag: 16oz
Under cover: 10oz
Space blanket under quilt: 10oz
Hennessy Asym tarp: 10oz
Total: 62oz (3lb. 14oz).
This was my first night in an open hammock without a bug screen and the air contact above was noticeably different-- felt more like sleeping outdoors. No bugs, and nice with no wind and moderate temps.
Conclusion? IMHO, pads inside a hammock suck. I am just not impressed. I would like to try a double layer hammock with a pad between. I have fiddled with a segmented pad extender, and it takes care of the side insulation issues, but it still feels lumpy and detracts from the natural comfort of the hammock surface.
I'd like to see a good pad solution. Of course under quilts will solve the problem, but pads are readily available and most people own them already. They are light, waterproof, durable and can be very cheap to purchase. They are little bulky, but they roll up and we've been dealing with packing them for decades now.
You can good quality damaged/leaky self-inflating pads for a song, although most are too narrow. You might be able cut up and combine two, with sections used sideways. You can make your own self-inflating pad with open cell foam and heat-seal fabric. In fact, a pad on the outside wouldn't need an airtight valve, as it would only have to inflate against the outer cover, not your weight. A Velcro flap would keep internal moisture to a minimum. It would be easy enough to attach a suspension. I wonder of it is possible to make a self-inflating pad with a differential cut, so it would take a curve? What you want is something like a section of a cone, or two intersection cones-- a large one for the upper torso and a longer, thinner one for the legs. and butt.
CCF pads could be cut in sections to assemble to a cone shape and joined with fabric joints/hinges.