I currently have a GoLite Poncho Tarp (Silnylon, 8 ft 8 in x 4 ft 10 in, 10.44oz on my scales), window insulation film as a ground sheet (1.10oz) and a Marmot Helium (16F, 31.82oz) or Atom (43F 21.52oz). I'm 5 feet 9 inches tall.
I do not use a bivy with my down bags and I haven't gotten wet.
My question is.... am I asking for trouble? Most other gear lists w/ poncho/tarps have lightweight or partial bivys included. I have slept through a decent rain storm or two, staying dry in A-frame pitch. But it's also relatively cramped under my little poncho/tarp, and I'm worried I'll get bit eventually. (I tried pitching in a half-pyramid for more protection in backyard, but was even more cramped length-wise and had trouble keeping it taught)
I am contemplating going lighter with Cuben Fiber products (solo tarp, poncho/tarp, bivy, pack) to lighten up.
If a bivy is recommended with an 8 ft 8 in x 4 ft 10 in poncho/tarp, I'll probably start weighing the pros/weights of a larger CF tarp vs. smaller tarp and bivy....or if there is a larger CF poncho/tarp than my current one.
Thanks for the advice. Currently sitting at ~8lbs base weight.