A recent post here concerning the downsizing of equipment (or, more accurately, reducing the weight of the equipment one carries on one's shooting excursions) starting the "wheels turning," as it were, on the issue of tripods. As an avid outdoorsman (sic), landscape and wildlife photographer, I do a lot of shooting with some of Nikon's longer and heavier glass (300mm F2.8 ED, 400mm F3.5ED, 500mm F4 P and 600mm F4ED lenses). To date, I have been using a heavy duty Manfrotto tripod (seriously modified) originally intended for use with a view camera. The unit performs well: it is rigid and holds the long glass rock steady. BUT, it is heavy, awkward, cumbersome and, in cold weather, just a PIA. So... I am looking for an upgrade as it were. I need something lighter,easier to operate in inclement weather, that I can strap onto my backpack, yet is capable of supporting the longer, heavier glass that I use. Suggestions?