I'm with Smokepole. Been running the same (SL5) for more than 15 years September through May in Idaho and Alaska. Floorless is not about weight for me, but functionality, and the colder the better it gets (I've been in mine down to 5 below). Wear boots into shelter, bigger footprint, taller center height, and heating option at little weight penalty. Notwithstanding some of the limitations mentioned above, I would much rather be shelter-bound in a tipi than similar weight floored shelter.
Get a Borah Bug bivy if the night creepers concern you.
