I would recommend that you at least evaluate an ultralight single wall tent as an alternative to the bivy. Outdoor Research makes one, the NightHaven Pocket Shelter, that is cheaper than the bivy and provides more protection against both the elements and small critters. It is essentially floorless, but a fitted floor is available. Try MoabSports.com and their $0.01 (US) buyer's club membership for good prices. The NightHaven appears to be out of stock at the moment, but they will honor their current prices on a backorder. I have had very good luck with them. +1 on the sleeping pad - more comfort and insulation.