I have a Thermarest Neo Xlite with an R value of 3.2 which I use most of the time.
I just bought an Onda II closed cell foam mat with an R value of 1.5-2. I bought it for mild-hot season hiking and as extra thermal protection when sleeping on Snow.
I would like of shorten the foam mat to about thigh length but not sure what affect it will have regarding heat lose when on snow with my Xlite on top.
Does anyone have any experience in this area? Will any part of my inflatable mat touching the ground mean I lose all insulation from the foam mat, or is it more of a relative thing. If the foam mat protects 80%, then I should still get 80% of the insulation, or my body will be fine but my feet will get cold...
FYI I currently use a 1mm foam mat that has a reflective lining with my Xlite on snow. I wouldn't say I wake up cold but I definately don't wake up warm either.
Maybe I need an Xtherm but hard to find that money when I'll only use it 2-3 nights some years.