i dunno about the space blanket and Spinn... your going to have some condensation problems...
i think you should be fine with just the SPE ..... i wouldn't try to get too crazy
that and putting that pad under the space blanket in the 2nd hammock i'll call it your going to find that the pad will have a problem forming to your body shape so you might not get the full benefit of the pad .... just a few problems i think you might run into..
but i say go for it and see what comes of it... never now might work
you said about liking Synth insulation... have you looked into AHE UQ ...
he makes some really nice UQ for around $125?
might be worth looking into