Tripod accessories

You do not need a portrait function when using your tripod head with a large telephoto lens, as you can do this using the adjusting screw on the tripod collar. But you will need a robust clamp for the horizontal and vertical planes -  if necessary also with resistance/friction adjustment, without any handle to get in the way, and without fluid damping or spring pre-tensioning. In this case, the VH tilt head is the right tripod head for you.