Hi all. I've owned the 300 mm f/4D AF-S since 2001 and I almost immediately after purchase added a secondary support to the wimpy tripod collar to get rid of the vibration problems at medium shutter speeds. It worked well but was inconvenient when going from horizontal to vertical shots and vice versa. Bjorn Rorslett on his website suggested an alternative collar made by Rainer Burzynski (available from www.isarfoto.com). I finally bought it last month and received it today. What is remarkable about it is that not only is it solid, it rotates really smoothly, takes very little space, and the foot of the leg fitts arca-swiss style QR systems directly without adding a QR plate to the bottom (reducing one potential source of movement). I also purchased an AS-style QR platform and a couple of plates for my bodies. Although I haven't yet taken pictures with it I want to say my first impressions after playing around with the following setup: Gitzo G1348, Kaiser ballhead, Burzysnki QR system and the 300/4 AF-S. It operates incredibly smoothly and there doesn't seem to be any slack whatsoever. When I lock the head, there is no appreciable movement after locking when I take my hands off the camera and lens. I've used Manfrotto heads and QR plates mostly to this point, and this system is really from another world. Why did I buy the collar even though I had the plastic secondary support? I got double image shots with my D70 and the older rig (Manfrotto 141 RC) when shooting at near-1/15th-sec speeds. I mean, the shots were absolutely useless, totally soft. I hadn't had problems before with other lenses and the lens (with 2ndary support) but this was just too much. I will shortly take some test shots for comparison at 1/15 s for you to see if I can manufacture the difference in inside conditions. I think there is wide interest in the 300/4 AF-S and I think the collar and QR system by RB should be of interest to those who have this lens.