Can anyone comment on the BA Double Z sleeping pad in regards to warmth, comfort, and durability? It's on sale on number of sites and I'm tempted to get one. I've been using a NeoAir (2.5" with 3.2 R-value), and while it's served me well for years, most nights I find myself struggling without being able to sleep on my side. My biggest concern is warmth--I like to hike in the high Sierra in CA (I've done the JMT and will probably do it again this summer), the Uintas in UT, and the Sawtooths in ID. I backpack late spring through early fall and have a 20 degree down bag and sleep in thermals. I haven't had issues with being cold in the past, but I've never slept on a mat with a lower R value before. Will I notice a big difference going down to the Double Z with a 1.5 R-value? The extra weight (and cost) of a more insulated 4" thick pad is enough of a deterrent to make me stick with what I have if the Double Z will leave me freezing.
Is the 4" Double Z that much more comfortable than something like the 2.5" thick NeoAir? Is it as durable? Would an emergency blanket under the pad help keep me warm on really cold nights?