I see you've got the Wimberly head and a heavy 400 mm so you need a big stable tripod. If you are going to carry your equipment any distance the two or three pounds you save with carbon fiber will seem worth it when you reach your destination. Do you really need a geared column, enough to endure the extra weight and expense? I'm using a 1548 now with my 600mm and I haven't missed the column, but I also haven't had that much experience.
Thanks For the info. I guess the gearded column was just a thought. Obregon, how do you move your 600mm lens? Do you use a Wimberley, if so is your lens attached directlt to the Wimberley or do you use a quick release plate? Do you use a ball head?
I use a Wimberley. (In fact, It's almost worth it to get big glass just so you can use the Wimberley; it's so smooth!) I have the quick release plate from Wimberley and a replacement foot for the Nikon 600 that Wimberley offers. This lowers the hight of the 600 and incorporates the ARCA swiss type plate. The 600 has a strap that goes with it, so if I'm going more than a few yards, I disconnect the lens and camera from the Wimberley, put the strap over my shoulder and put the tripod on the other shoulder, or carry it in my hand.
I've got an Arca Swiss Ballhead on a Manfrotto 441 Carbon Fiber tripod that I use for shorter lenses including an 80-400 VR.
Of course, if I'm using the 600 I don't carry much else except a teleconverter, film and a cable release in my pocket. Art Morris claims he carries both his 600mm, a gitzo tripod and his canon 400 mm IR (I think that's the right nomenclature) but Art seems at least 6'2" so maybe he can do it.
I use a 500mm, and also have the G1548 without a center column. I don't use a center column on either of my tripods, and I never had the feeling I missed one. I consider a tripod with extended center column more as as a monopod.
I know you asked PHil, but I want to add my 2 cents. I hate the circular leg tighteners and much prefer levers. On a couple of occasion I couldn't release a tightener in the field and carried the tripod home only partly closed. Strangely enough, when I got home release proved easy. However, given that the 1548 is as stable as a rock under big lenses, it's an inconvenience that I tolerate.
I hated the circular tightening measures (is that how you call in in English?) on the older models, as they where just half as large than the newer models. You could only use thumb and forefinger to untighten the screw, and often this caused some problems. With the newer ones, you can put three or four fingers around, which makes it a lot easier to untighten them.