hangman, et al,
Interesting approach.... Thanks for testing and reporting on it.
Come to think of it, this approach is not unlike a vapor barrier approach.... That suggests yet another option on this gear for really cold weather.... the HH under pad could also be placed outside of the silnyl cover and under the Nest... This would protect it from body moisture inside the HHSS.
Of course like all vapor barrier approaches you'll need to deal with the moisture issues of the vapor barrier inside the hammock and with your top bag/quilt.
Let the testing begin.... Remember to have a safe bail out plan.