I ended up getting cold last night. I tried my Prolite plus pad in the hammock and although the Burrow 40 was at the very end of its range, it was the lack of coverage by the pad that got me. Anywhere I got off the the pad was quickly cold. The el cheapo, but light foam pad will probably work the best.
I did try my primaloft UQ and it worked pretty well, but it would work better if it was designed specifically to fit.