>I have just recently completed a Speer Hammock kit and it rides great. For now, I am planning on just 3 season use.
I did a bit of testing before I took my hammock out in the winter. The results might be of use to you, although the temp range for most of the tests was much colder. I posted the details in this thread.
>Question: will the following setup take me relatively comfortably to 45F?
>-Speer Top Blanket II, 1.5 in loft.
>-Smartwool microweight shirt and long johns
I use a Jacks R Better Nest 2.5-inch down quilt over synthetic underwear to below +40F, so I think this will work. You'll probably carry an insulated clothing layer as well, and you can always lay that on top if you're a bit cold.
>-2 sheets of 1/8" Speer evazote-type foam, one full length, one doubling the width at the torso.
This should work. I've used a single Gossamer Gear ThinLight 1/8" pad (Evazote) down to +40F, but I was also wearing my Patagonia Micropuff pull-over. Your extra pad will provide more insulation than my crushed Polarguard. I find that pads in the hammock are a bit of a pain to arrange, but it should be easier to place them in your Speer hammock than in a Hennessy. You may get some condensation on the pads, but hopefully most of the moisture will go out through the top quilt. Your wool base layer will help with that.
>I will initially take backup warmth while I explore the range of this setup. Am I pushing it?
I think your setup will be about right for lows of +45F, so with backup warmth (such as a fleece clothing layer and maybe a fleece blanket) you should be able to test those temps and colder in comfort.
> Would loosely attaching poncho to the bottom as a windblock provide much benefit?
A bit. If the wind is getting in around your pads (unlikely, if you tuck in your top quilt) or you're feeling cold spots where you have only one layer of pad, then I'd give it a try. I'd sling it close rather than loose to reduce convection. I know others with the Hennessy Hammock SuperShelter just use the silnylon under-cover as their bottom insulation in warm weather, so the poncho would be equivalent. I recommended bringing a fleece blanket as backup while testing. If you are cold, using the poncho to sling this blanket closely under the hammock will probably add 20F to the comfort range.
If you find having pads in the hammock annoying or if there is too much condensation accumulating on the pads and chilling your skin, you can use the poncho to sling the pads underneath the hammock.
If possible, spend a few nights in the back yard or a local park. You can quickly test several different configurations with the convenience of being able to bail if you get too cold, and then you won't have to carry much backup warmth weight on your trip.