Unfortunately, the Nikon 600mm f1/4E FL ED VR does not balance with the D810 and the foot replacement LCF-13 by Really Right Stuff nor with the Nikon stock foot. The LCF-13 worked perfectly with the previous model 600mm f1/4G ED VR.
After some research I ordered the foot LF-N604FL by jobu design. It is 4 cm longer than the Nikon stock foot and 2cm longer than the new LCF-18 by RRS, which is too short according to this comment. Now, my setup balances fine horizontally, but vertically the lens sits (still) too high with the gimbal by Dietmar Nil.
To balance my setup also vertically, I needed a different gimbal head. The WH-200 Wimberley Head Version II would let me compensate a height up to 12 cm. I went with the Jobu Heavy Duty MK IV, which is a bit lighter, but only gives you about 10.5 cm (my combination requires at least 10 cm).
Update 04.03.2017: Perfectly balancing a Nikon 600mm FL with a D810 / D500 works now. I not only replaced the stock foot, but also use the gimbal Heavy Duty MK IV by jobu design.
Update 23.04.2016: Balancing the 600mm FL horizontally works fine now. I finally went with a foot replacement by jobu design.
Update 06.11.2015: A few words about my setup in the video. I replaced the stock foot of the lens with the RRS LCF-13, which has a lower profile, is lighter than the original Nikon foot and even slighly longer. The tripod head is by Dietmar Nill and weights 1.2kg. Unfortunately height can not be addjusted, but it’s less extrem than it seems in the video. Note that the exact same setup worked perfectly fine on the older 600mm F/4 ED VR.
I just got my Nikon 600mm f/4 FL ED VR a few days ago. It’s so light and you can really handhold it. But the initial smile after picking it up went away pretty quickly as soon as I mounted it on my tripod with the D810 attached. It’s not possible to balance it! It’s way too front-heavy.
Only after not only attaching the additional battery grip MD-12, but also loading it with AA batteries, did I manage to balance it. The normal EN-EL15 was not enough.
How can this be? What an oversight by Nikon! I bought this lens because it’s light, and now I have to add weight back to make it work properly. What an irony!
This actually means that it only works properly with the heaviest camera, the D4. It also means that Nikon can’t make lighter flagship bodies in the future as long as they still want to support this lens.
The only solution I see without having to completely redesign the lens, is to drastically reduce the weight of the hood. Good opportunity for any 3D printing business. I’d buy one.