I occasionally take the odd shot of a bird and as I like to take pictures hand held, I struggle with f8, 600mm and a crop camera, but 1344mm!! Wow. I cant even imagine how you line that up. Do you use a very expensive ball head? and also an extremely stable tripod (possibly weighed down with large blocks of lead on each leg)
Practice and the right gear. I use my 1D4, 600mm f/4 IS II + 1.4III, Wimberley II, and a Girzo GT5542LS. No lead required. Framing takes practice but the setup I just described makes it really easy. The support is a very important part of successfully using long focal lengths.